Heat sinking and flexible circuit board, for solid state light fixture utilizing an optical cavity

ABSTRACT

Disclosed exemplary solid state light fixtures use optical cavities to combine or integrate light from LEDs or the like. In such a fixture, the cavity is formed by a light transmissive structure having a volume, and a diffuse reflector that covers a contoured portion of the structure. A circuit board has flexible tabs mounting the light emitters. A heat sink member supports the circuit board and is contoured relative to the shape of the light transmissive structure so that the tabs bend and the emitters press against a sufficiently rigid periphery of the light transmissive structure. TIM may be compressed between the heat sink member and the opposite surface of each tab. Various contours/angles of the periphery of the light transmissive structure and the mating portion of the heat sink member may be used.

RELATED APPLICATION

This application is a continuation in part of U.S. application Ser. No.12/434,248 Filed May 1, 2009 entitled “Heat Sinking and Flexible CircuitBoard, for Solid State Light Fixture Utilizing an Optical Cavity,” thedisclosure of which is entirely incorporated herein by reference.

TECHNICAL FIELD

The present subject matter relates to solid state type light fixtureseach having an optical cavity formed by a light transmissive volume,which may be filled with a liquid or solid, and more specifically, totechniques for mounting the solid state light emitters in relation tothe structure, electrically connecting the solid state light emittersand providing effective heat dissipation for such light emitters.

BACKGROUND

As costs of energy increase along with concerns about global warming dueto consumption of fossil fuels to generate energy, there is an everyincreasing need for more efficient lighting technologies. These demands,coupled with rapid improvements in semiconductors and relatedmanufacturing technologies, are driving a trend in the lighting industrytoward the use of light emitting diodes (LEDs) or other solid statelight sources to produce light for general lighting applications, asreplacements for incandescent lighting and eventually as replacementsfor other older less efficient light sources.

To provide efficient mixing of the light from a number of sources and apleasing uniform light output, Advanced Optical Technologies, LLC (AOT)of Herndon, Va. has developed a variety of light fixture configurationsthat utilize a diffusely reflective optical integrating cavity toprocess and combine the light from a number of solid state sources. Byway of example, a variety of structures for AOT's lighting systems usingoptical integrating cavities are described in U.S. Patent ApplicationPublications 2007/0138978, 2007/0051883 and 2007/0045524, thedisclosures of which are incorporated herein entirely by reference.

Although these integrating cavity-based lighting systems/fixturesprovide excellent quality light in an efficient manner and address avariety of concerns regarding other solid state lighting equipment,there is still room for improvement. For example, efficiency of theoptical integrating cavity decreases if the diffuse reflectivity of itsinterior surface(s) is compromised, for example due to contaminationfrom dirt or debris entering the cavity. Also, since the cavity isfilled with air (low index of refraction), some light may be trapped inthe LED packages by internal reflection at the package surface becausethe material used to encapsulate the LED chip may have a higher index ofrefraction. Efficiency may also be somewhat reduced if the mask orportion of the cavity around the aperture needs to have a relativelylarge size (producing a small optical aperture) to sufficiently reduceor prevent direct emissions from the solid state light source(s) throughthe cavity and optical aperture.

U.S. Patent Application Publications 2008/0094835 to Marra et al.describes a light engine having a chamber with an aperture and a numberof LED elements positioned inside the chamber. Inner surfaces of thechamber are highly-reflective and essentially non-absorbing towardslight within a desired wavelength region. The reflective inner surfacesare formed by a diffuse-reflective material sandwiched between asubstrate/wall and a transparent covering plate. To improve efficiencyof light extraction from the LEDs, the fixture may include out-couplingelements that are optically coupled between the LEDs and the transparentcovering plate. Although the cavity may be empty, this publication alsosuggests that the cavity may be filled with a material which has arefractive index that approaches or, preferably, matches the refractiveindex of one or more of the other elements of the light engine, e.g.that of the transparent covering plate. As disclosed, this fillermaterial may be an organic medium such as a transparent liquid,particularly an oil, or a solid resin, particularly a silicone resin,possessing the desired (matching) refractive index, and which ispreferably substantially non-absorbing with respect to visible lightand/or with respect to the light generated inside and emitted from theLED dies.

U.S. Pat. No. 7,040,774 to Beeson et al discloses an illumination systemhaving one or more LEDs and a wavelength conversion layer within alight-recycling envelope. In some examples, the wavelength conversionlayer may fill a substantial portion of the volume of thelight-recycling envelope. The light from the LED source(s) istransmitted through the wavelength conversion layer in order to converta portion of the light of a first wavelength range into light of asecond wavelength range. Light of both the first and second wavelengthranges exit the light-recycling envelope through an aperture.

These developments not withstanding, in this age of ever increasingconcern over energy consumption, there is always a need for techniquesto still further improve efficiency of solid state lighting fixtures orsystems. Also, any modification of the structure or design of the solidstate light fixture must address ancillary issues, such as circuitmounting and/or heat dissipation. For example, LED type solid stateemitters generate heat, and it is important to provide effective heatdissipation to avoid damage to the LEDs or associated circuitry.

SUMMARY

The teachings herein address one or more of the needs outlined abovewith regard to improvements in solid state light fixtures or lightingsystems using a diffusely reflective optical cavity to combine orintegrate light from the emitters. For example, the arrangementsdiscussed herein provide connections to and mounting for solid statelight emitters in a manner that provides efficient light coupling intothe optical cavity and provides efficient heat dissipation. A flexiblecircuit board mounted on a heat sink member has one or more flexibletabs on which the emitter(s) are mounted. When installed in the fixture,each tab bends and the emitter(s) for example may press against aperipheral surface of a light transmissive structure forming the volumefor an optical cavity.

The detailed descriptions and drawings disclose various examples oflight fixtures and lighting systems, for providing general lighting in aregion or area intended to be occupied by a person.

A light fixture, for example, might include a light transmissivestructure forming a volume. In this example, the structure has acontoured outer surface, an optical aperture surface and a peripheraloptical coupling surface between the contoured outer surface and theoptical aperture surface. The peripheral optical coupling surface formsan obtuse angle with respect to the optical aperture surface. Areflector included in the fixture provides a diffusely reflectiveinterior surface extending over at least a substantial portion of thecontoured outer surface of the light transmissive structure, to form anoptical cavity including the volume of the light transmissive structure.A portion of the aperture surface of the light transmissive structureforms an optical aperture for passage of light out of the cavity. Theexemplary fixture also includes a heat sink member with an innerperipheral portion of a size somewhat larger than the outer peripheralportion of the light transmissive structure. This heat sink member hasan inner surface at an angle at least substantially corresponding to theangle formed by the peripheral optical coupling surface of the lighttransmissive structure. The exemplary fixture also includes a flexiblecircuit board, which has a mounting section mounted on the heat sinkmember, and at least one flexible tab attached to and extending from themounting section. Each flexible tab bends around the heat sink memberinto a position between the angled inner surface of the inner peripheralportion of the heat sink member and the angled peripheral opticalcoupling surface of the light transmissive structure. The fixture alsohas one or more solid state light emitters, for producing lightintensity sufficient for a general lighting application of the fixture.At least one solid state light emitter is mounted on a respective tab ofthe flexible circuit board. The respective tab positions the emitter itsupports between the tab and the angled peripheral optical couplingsurface of the outer peripheral portion of the light transmissivestructure. The tab holds the solid state light emitter against theperipheral optical coupling surface of the light transmissive structurefor emission of light through that surface into the volume formed by thelight transmissive structure.

The detailed disclosure also describes a variety of features that may beincorporated into different examples of such a fixture or light engine.For example, at least a substantial portion of the contoured outersurface of the light transmissive structure has a roughened or etchedtexture. In such an implementation, at least any portion of the angledperipheral optical coupling surface of the light transmissive structurereceiving light from the one or more solid state light emitters likelywould be highly transparent. Although the aperture surface may be highlytransparent, it is also contemplated that at least a substantial portionof the optical aperture surface of the light transmissive structure hasa roughened or etched texture.

In some examples of the light fixture, there are one or more vias formedthrough each respective tab, from a first surface of the respective tabsupporting the solid state light emitter to an opposite second surfaceof the respective tab. Heat conductive material extends through each viafrom the first surface to the second surface of the respective tab, toconduct heat from each solid state emitter on the respective tab. In atypical implementation of such an exemplary circuit board, heatconductive pads are also formed on the first and second surfaces of eachtab. The heat conductive pad on the first surface contacts each lightemitter on the respective tab; and the heat conductive pad on the secondsurface transfers heat to the heat sink member. The heat conductivematerial extending through each via through each respective tab conductsheat from each solid state emitter on the respective tab, from the firstpad on the respective tab to the second pad on the respective tab fortransfer to the heat sink member.

The fixture may also include thermal interface material (TIM) positionedbetween the respective tab and the angled inner surface of the innerperipheral portion of the heat sink member. The TIM may provideelectrical insulation between the tabs and the heat sink member, forexample, for an implementation in which a heat slug of an emitter isconductive. The TIM, however, also provides thermal conductivity to theheat sink member. In such an example, pressure created by contact of atleast one solid state light emitter with the angled outer peripheraloptical coupling surface of the light transmissive structure compressesthe TIM against the heat sink member.

In current implementations, a fixture includes a plurality of solidstate light emitters which typically are light emitting diodes (LEDs).Various combinations of different colors of LEDs may be used, forexample RGB LEDs or combinations of white LEDs with other LEDs. In theillustrated example of the circuitry, each LED is a white LED.

The present discussion encompasses a variety of different structuralconfigurations for the light transmissive structure. Several examplesare shown and described in which the light transmissive structurecomprises a light transmissive solid substantially filling the volume ofthe light transmissive structure. Materials containing phosphors may beprovided within or around the solid. For example, the structure mayutilize two pieces of the light transmissive solid with a gaptherebetween, filled with a phosphor or phosphor bearing material. Suchan arrangement may position the phosphor somewhat near the middle of thevolume of the light transmissive structure, or at least one of the lighttransmissive sections may be located at the optical aperture surface ofthe light transmissive structure, so as to position the phosphor at ornear the optical aperture. As another alternative, the lighttransmissive structure may comprise a container. Although the containercould be filled with a gas, in an illustrated example, the container isfilled with a liquid. The liquid may contain a phosphor, such as one ormore nano phosphors.

In the illustrated examples, the diffuse reflections of light within thevolume of the light transmissive structure optically integrate lightfrom the solid state light emitters. The fixture emits opticallyintegrated light through the optical aperture, at the aperture surfaceof the light transmissive structure. In the examples, the emissionsthrough the aperture create a virtual source of light at the aperture,exhibiting substantially uniform light intensity across the area of theaperture.

In some examples, each tab holds one or more light emitters against theperipheral optical coupling surface of the light transmissive structurefor emission of light through the peripheral optical coupling surface.The orientation of each emitter is such that the aperture surface of thelight transmissive structure reflects a portion of direct emissions fromthe solid state light emitter back into the optical cavity by totalinternal reflection, for subsequent diffuse reflection off of thereflector for optical integration within the cavity before emissionthrough the optical aperture.

In some examples shown, the tabs hold light emitters against the outerperipheral portion along the contoured surface of the light transmissivestructure in such an orientation that the central axis of emission ofeach light emitter is substantially at a right angle to theperpendicular axis of the aperture surface of the light transmissivestructure and therefore substantially parallel to the aperture surfaceof the light transmissive structure. In other examples, the respectivetab holds at least one solid state light emitter in such an orientationthat the central axis of emission of the light emitter is substantiallyat an acute angle relative to the axis of the aperture surface of thelight transmissive structure and inclined somewhat away from theaperture surface of the light transmissive structure. In one specificexample, the obtuse angle of the peripheral optical coupling surfacewith respect to the optical aperture surface of light transmissivestructure is approximately 120° and the acute angle of the central axisof emission of each light emitter relative to the axis of the aperturesurface of the light transmissive structure approximately 60°.

The light fixture may include a mask having a reflective surface facinginward with respect to the volume, covering a portion of the aperturesurface of the light transmissive structure in proximity to the solidstate light emitters. The optical aperture is formed by a portion of theaperture surface not covered by the mask. However, the arrangement ofthe aperture surface and the emitters to facilitate reflection of directemissions via TIR allows use of a relatively narrow mask, or in someconfigurations may allow elimination of the additional mask, yet stillenable sufficient diffuse reflections within the cavity/volume as toprovide adequate optical integration of the light from the emitters,e.g. to provide the virtual source output at the aperture.

The volume of the light transmissive structure, and thus the opticalcavity of the fixture, may have any shape providing adequate reflectionswithin the volume/cavity for a particular application. Examples havingshapes corresponding to a portion or segment of a sphere or cylinder arepreferred for ease of illustration and/or because curved surfacesprovide better efficiencies than other shapes that include more edgesand corners which tend to trap light. Hence, in the illustratedexamples, the volume of the light transmissive structure has a shapecorresponding to a substantial section of a sphere, e.g. a hemisphere.The outer peripheral portion of the structure along the contouredsurface of the light transmissive structure is circular, as are theinner peripheral portion of the mounting section of the flexible circuitboard and the inner peripheral portion of the heat sink member.

To further improve efficiency, it may help with coupling of light fromthe emitters into the light transmissive solid to provide an opticalgrease, glue or gel between the peripheral optical coupling surface andat least one solid state light emitter. This material eliminates airgaps and/or provides refractive index matching relative to a material ofthe light transmissive structure, for example, the material forming theangled peripheral optical coupling surface of the light transmissivestructure.

The present disclosure also encompasses various solid state lightingsystems. An example of such a system might include a light fixture anddrive circuitry. For example, the fixture might include a lighttransmissive structure forming a volume. The structure has a contouredouter surface and an optical aperture surface. A reflector included inthe fixture provides a diffusely reflective interior surface extendingover at least a substantial portion of the contoured outer surface ofthe light transmissive structure, to form an optical cavity includingthe volume of the light transmissive structure. A portion of theaperture surface of the light transmissive structure forms an opticalaperture for passage of light out of the cavity. The fixture alsoincludes a heat sink member having an inner peripheral portion of a sizesomewhat larger than an outer peripheral portion of the lighttransmissive structure. The inner peripheral portion of the heat sinkmember has an inner surface at least substantially conforming in shapeto the outer peripheral portion of the light transmissive structure. Inthis exemplary system, the fixture also includes a flexible circuitboard. Here, the flexible circuit board has a mounting section mountedon the heat sink member and a strip extending from the mounting sectionof the flexible circuit board providing electrical connections to thedrive circuitry. The flexible circuit board also includes at least oneflexible tab attached to and extending from the mounting section of theflexible circuit board. Each flexible tab bends around the heat sinkmember to position a portion of the tab that supports a solid statelight emitter between the inner surface of the inner peripheral portionof the heat sink member and the outer peripheral portion of the lighttransmissive structure. One or more solid state light emitters arecapable of producing light intensity sufficient for a general lightingapplication of the fixture. A respective tab holds at least one solidstate light emitter against the outer peripheral portion of the lighttransmissive structure for emission of light into the volume formed bythe light transmissive structure.

The exemplary arrangements hold the solid state light emitters in amanner that allows improved optical performance as well as efficientheat dissipation. Also, the combination of the heat sink member and theflexible circuit board, sized appropriately in relation to theperipheral portion of the light transmissive structure facilitatesassembly of the light fixture during manufacture.

Additional advantages and novel features will be set forth in part inthe description which follows, and in part will become apparent to thoseskilled in the art upon examination of the following and theaccompanying drawings or may be learned by production or operation ofthe examples. The advantages of the present teachings may be realizedand attained by practice or use of various aspects of the methodologies,instrumentalities and combinations set forth in the detailed examplesdiscussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1 is a cross-sectional view of a solid state light fixture, havinga solid-filled optical integrating cavity, which is useful in explainingseveral of the concepts discussed herein.

FIG. 2 is a cross-sectional view of a one-piece solid construction ofthe light transmissive structure, used in the fixture of FIG. 1.

FIG. 3 is an enlarged portion of the cross-section of the fixture ofFIG. 1, showing several elements of the fixture in more detail.

FIG. 4 is a bottom view of the solid state light fixture of FIG. 1.

FIG. 5 is a top plan view of an LED type light fixture, illustrating aproduct that embodies a number of the concepts discussed herein.

FIG. 6 is an isometric view of the LED type light fixture of FIG. 5.

FIG. 7 is an end view of the LED type light fixture of FIG. 5.

FIG. 8 is a side view of the LED type light fixture of FIG. 5.

FIG. 9 is a cross-sectional view of the LED type light fixture of FIG.5, taken along line A-A of the end view of FIG. 7.

FIG. 10 is a bottom view of the LED type light fixture of FIG. 5.

FIG. 11 is a plan view of the flexible circuit board used in the LEDtype light fixture of FIG. 5.

FIG. 12 is a side view of the flexible circuit board of FIG. 11.

FIG. 13 is a plan view of the flexible circuit board, but showing howflexible elements of the board are bent or curved as if installed in theLED type light fixture of FIG. 5.

FIG. 14 is a side view of the flexible circuit board, but showing howflexible elements of the board are bent or curved as if installed in theLED type light fixture of FIG. 5.

FIG. 15 is a bottom plan view of the heat sink ring of the LED typelight fixture of FIG. 5.

FIG. 16 is an end view of the heat sink ring of FIG. 15.

FIG. 17 is a side view of the heat sink ring of FIG. 15.

FIG. 18 is an isometric view of the heat sink ring of FIG. 15.

FIG. 19 is a cross-sectional view of an alternative construction of thelight transmissive structure, for use in the fixture of FIG. 1, in whichthe structure is formed of two transmissive solid members with aphosphor filled gap formed therebetween.

FIG. 20 is a cross-sectional view of an alternative construction of thelight transmissive structure, for use in the fixture of FIG. 1, in whichthe structure is formed of a liquid-filled container forming the volumeand optical cavity.

FIG. 21 is a cross-sectional view of yet another alternativeconstruction of the light transmissive structure, for use in the fixtureof FIG. 1, in which the light transmissive structure contains a phosphorat or near the aperture surface.

FIGS. 21A and 21B are detailed views of the cross-section in region B-Bof FIG. 21, wherein the phosphor containment at or near the aperture isimplemented in two somewhat different ways.

FIG. 22 is a cross-sectional view of another example of an LED typelight engine or fixture, having a solid-filled optical integratingcavity.

FIG. 23 is a cross-sectional view of a one-piece solid construction ofthe light transmissive structure, used in the fixture of FIG. 22.

FIGS. 24 to 29 are various other views of the LED type light fixture ofFIG. 22.

FIG. 30 is a top plan view of the heat sink ring of the LED type lightfixture of FIG. 22.

FIG. 31 is a side view of the heat sink ring of FIG. 30.

FIG. 32 an isometric view of the top of the heat sink ring of FIG. 30.

FIG. 33 an isometric view of the bottom of the heat sink ring of FIG.30.

FIG. 34 a cross-sectional view of a light incorporating the engine orfixture of FIG. 22 with housing components and a secondary optic, inthis case, a reflector coupled to the aperture.

FIG. 35 is a functional block type circuit diagram, of an example of thesolid state lighting elements as well as the driver circuitry, controland user interface elements which may be used with any of the fixtureconfigurations to form an overall lighting system.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, components,and/or circuitry have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

Various concepts discussed below relate to heat sink and circuit boardarrangements for solid state type light fixtures. Each fixture has anoptical cavity formed by a light transmissive volume, which for examplemay be filled with a liquid or a solid, and a reflector covering asubstantial portion of a contoured surface of the light transmissivestructure that forms the volume of the cavity. A flexible circuit boardis mounted on a heat sink member. One or more tabs of the flexiblecircuit board provide support and electrical connection for one or moresolid state light emitters. When installed in the fixture, each tabbends to locate the emitter(s) between the light transmissive structureand the tab/heat sink member. In the examples, variations of thisarrangement press one or more of the solid state light emitters againsta periphery of the light transmissive structure forming the volume forthe optical cavity. In at least one example, the periphery comprises anangled surface. The emitter contact provides optical coupling of lightfrom each emitter into the optical volume for diffuse reflection in thecavity. However, the positioning between the light transmissivestructure and the heat sink member also facilitates heat transfer fromthe emitters to the heat sink, and thus dissipation of the heatgenerated during operation of the light fixture.

Reference now is made in detail to the examples illustrated in theaccompanying drawings and discussed below. FIG. 1 is a somewhat stylizedrepresentation of a cross-section of a first example of a light fixtureor “light engine” apparatus 1 intended for general lighting, forexample, in a region or area intended to be occupied by a person. FIG. 2is a cross-sectional view of a one-piece solid construction of the lighttransmissive structure 6 that forms the optical volume 2, in the fixture1 of FIG. 1. FIG. 3 is a detailed/enlarged view of a portion of thegeneral lighting fixture 1, useful in explaining aspects of the flexiblecircuit board 11 and heat sink member 13. FIG. 4 is a bottom view(‘bottom’ in terms of the exemplary downlight orientation of FIG. 1) ofthe light fixture 1. These and other drawings are not drawn to scale. Inmost of the examples, for convenience, the lighting apparatus is shownin an orientation for emitting light downward. However, the apparatusmay be oriented in any desired direction to perform a desired generallighting application function.

Examples of general lighting applications include downlighting, tasklighting, “wall wash” lighting, emergency egress lighting, as well asillumination of an object or person in a region or area intended to beoccupied by one or more people. A task lighting application, forexample, typically requires a minimum of approximately 20 foot-candles(fcd) on the surface or level at which the task is to be performed, e.g.on a desktop or countertop. In a room, where the light fixture 1 ismounted in or hung from the ceiling or wall and oriented as a downlight,for example, the distance to the task surface or level can be 35 inchesor more below the output of the light fixture. At that level, the lightintensity will still be 20 fcd or higher for task lighting to beeffective.

The fixture 1 includes a light transmissive structure 6 forming a volume2. As shown in FIG. 2, the structure 6 has a contoured outer surface 6 cand an optical aperture surface 10. At least an outer peripheral portion6 p of the structure 6 along the contoured surface 6 c is substantiallyrigid. The contoured surface 6 c, at least in regions where there is nocontact to a solid state light emitter 5, has a roughened or etchedtexture.

As discussed in detail with regard to FIGS. 1 to 4, but applicable toall of the examples, hemispherical shapes for the light transmissivestructure and volume are shown and discussed, most often forconvenience. Hence, in the example of FIGS. 1 to 4, contoured outersurface 6 c approximates a hemisphere, and the optical aperture surface10 approximates a circle. Examples having shapes corresponding to aportion or segment of a sphere or cylinder are preferred for ease ofillustration and/or because curved surfaces provide better efficienciesthan other shapes that include more edges and corners which tend to traplight. Those skilled in the art will understand, however, that thevolume of the light transmissive structure, and thus the optical cavityof the fixture, may have any shape providing adequate reflections withinthe volume/cavity for a particular application.

Hence, the exemplary fixture 1 uses a structure 6 forming asubstantially hemispherical optical volume 2. When viewed incross-section, the light transmissive structure 6 therefore appears asapproximately a half-circle. This shape is preferred for ease ofmodeling, but actual products may use somewhat different curved shapesfor the contoured portion 6 c. For example, the contour may correspondin cross section to a segment of a circle less than a half circle orextend somewhat further and correspond in cross section to a segment ofa circle larger than a half circle. Also, the contoured portion 6 c maybe somewhat flattened or somewhat elongated relative to the illustratedaxis of the aperture 4, the aperture surface 10 and the exemplary solid6 (in the vertical direction in the exemplary downlight orientationdepicted in FIGS. 1 and 2).

In the example, the aperture surface 10 is shown as a flat surface.However, those skilled in the art will recognize that this surface 10may have a convex or concave contour. Typically, the surface 10 isclear-transparent, although the surface could have a diffuselytranslucent finish or be covered by a transmissive white diffuser or thelike.

Although other arrangements of the light transmissive structure arediscussed more, later, in this first example, the light transmissivestructure forming the volume 2 comprises a one piece light transmissivesolid 6 substantially filling the volume 2. Materials containingphosphors may be provided within or around the solid, as will bediscussed more, later. In the example of FIGS. 1 to 4, the solid 6 is asingle integral piece of light transmissive material. The material, forexample, may be a highly transmissve and/or low absorption acrylichaving the desired shape. In this first example, the light transmissivesolid structure 6 is formed of an appropriate glass.

The glass used for the solid of structure 6 in the exemplary fixture 1of FIG. 1 is at least a BK7 grade or optical quality of glass, orequivalent. For optical efficiency, it is desirable for the solidstructure 6, in this case the glass, to have a high transmissivity withrespect to light of the relevant wavelengths processed within theoptical cavity 2 and/or a low level of light absorption with respect tolight of such wavelengths. For example, in an implementation using BK7or better optical quality of glass, the highly transmissive glassexhibits 0.99 internal transmittance or better (BK7 exhibits a 0.992internal transmittance).

The fixture 1 also includes a reflector 3, which has a diffuselyreflective interior surface 3 s extending over at least a substantialportion of the contoured outer surface 6 c of the light transmissivestructure 6. For optical efficiency, there is little or no air gapbetween the diffusely reflective interior surface 3 s of the reflector 3and the corresponding portion(s) of the contoured outer surface 6 c ofthe light transmissive structure 6. In this way, the diffuse reflectivesurface 3 s forms an optical cavity from and/or encompassing the volume2 of the light transmissive structure 6, with an optical aperture 4formed from a portion or all of the aperture surface 10 of the lighttransmissive structure 6.

It is desirable that the diffusely reflective surface(s) 3 s of thereflector 3 have a highly efficient reflective characteristic, e.g. areflectivity equal to or greater than 90%, with respect to the relevantwavelengths. Diffuse white materials exhibiting 98% or greaterreflectivity are available, such as Spectralon® and Duraflect®. Theillustrated example of FIGS. 1 to 4 utilizes Valar® as the reflector 3.Valar® initially comes in flat sheet form but can then be vacuum formedinto desired shapes, in this case, into a dome shape conforming to thecontoured outer surface 6 c of the light transmissive structure 6. Thoseskilled in the art will recognize that other materials may be utilizedto construct the reflector 3 to have the desired shape and opticalperformance. Various reflective paints, powders and sheet materials maybe suitable. The entire interior surface 3 s of the reflector 3 may bediffusely reflective, or one or more substantial portions may bediffusely reflective while other portion(s) of the surface may havedifferent light reflective characteristics, such as a specular orsemi-specular characteristic.

At least a portion 4 (FIG. 1) of the aperture surface 10 of the lighttransmissive structure 6 serves as a transmissive optical passage oreffective “optical aperture” for emission of integrated light, from theoptical integrating volume 2, in a direction to facilitate theparticular general lighting application in the region or area to beilluminated by the light fixture (generally downward and/or outward fromthe fixture in the orientation of FIG. 1). The entire surface 10 of thesolid structure 6 could provide light emission. However, the example ofFIG. 1 includes a mask 9 having a reflective surface facing into theoptical integrating volume 2, which somewhat reduces the surface areaforming the transmissive passage to that portion of the surface shown at4. The optical volume 2 operates as an optical integrating cavity(albeit one filled with the light transmissive solid of structure 6),and the passage 4 for light emission forms the optical aperture of thatcavity.

As noted, the surface of the mask 9 that faces into the opticalintegrating volume 2 (faces upward in the illustrated orientation) isreflective. That surface may be diffusely reflective, much like thesurface 3 s, or that mask surface may be specular, quasi specular orsemi-specular. Other surfaces of the mask 9 may or may not bereflective, and if reflective, may exhibit the same or differenttypes/qualities of reflectivity than the surface of the mask 9 thatfaces into the optical integrating volume 2.

In the example, the light fixture 1 also includes one or more solidstate light emitters 5, which provide light intensity sufficient for aparticular general lighting application intended for the light fixture.An emitter 5 may be any appropriate type of light emitting semiconductorbased device. In the specific examples discussed herein the solid statelight emitters are light emitting diodes (LEDs). The present teachingsencompass use of various types/colors of LEDs, such as red (R), green(G) and blue (B) LEDs, ultraviolet (LEDs) to pump phosphors in thefixture, LEDs of two or more different color temperatures of whitelight, etc. Various combinations of different colors of LEDs may beused. However, for simplicity, the discussion of this example willassume that the LED type solid state light emitters 5 are white lightLEDs rated to all emit the same color temperature of white light. Hence,in the illustrated example of the circuitry (FIG. 35 as discussed,later), each LED is a white LED of the same or similar model. As noted,there may be as few as one solid state emitter, however, forillustration and discussion purposes, we will assume in most instancesbelow that the fixture includes a plurality of solid state emitters.

An optical grease, glue or gel of an appropriate refractive index may beapplied between the light emitting surfaces of the LED type solid stateemitters 5 and the corresponding segments of the outer peripheralportion 6 p along the contoured surface 6 c of the light transmissivestructure 6. Use of such a grease may improve optical extraction oflight from the package encapsulating the LED chip and thus the couplingof light from each emitter into the light transmissive structure 6.

The exemplary light fixture 1 also includes a flexible circuit board 11.As shown in greater detail in FIG. 3, the flexible circuit board 11 hasa mounting section or region 11 p that is at least substantially planar(and is therefore referred to herein as a “planar” mounting section) forconvenience in this example. As shown in the bottom view of FIG. 4, theplanar mounting section 11 p has an inner peripheral portion 11 i. Inthis first example, the solid forming the light transmissive structure 6is roughly or substantially hemispherical, and the lower periphery iscircular. The inner peripheral portion 11 i of the flexible circuitboard 11 has a shape substantially similar to the shape of the outerperiphery 6 p of the light transmissive structure 6, that is to say acircular shape in the example. The circular inner peripheral portion 11i of the flexible circuit board 11 has a size slightly larger than thecircular outer peripheral portion of the light transmissive structure 6.The flexible circuit board 11 also has flexible tabs 11 t (FIGS. 1 and3) attached to and extending from the inner peripheral region of theflexible circuit board 11. As is shown in FIGS. 3 and 4, a portion 11 cof each tab forms a curve.

The number and type of LED type solid state light emitters 5 used in thefixture are selected so as to produce light intensity sufficient for ageneral lighting application of the fixture 1. The emitters 5 aremounted on the tabs 11 t. At least one of the solid state light emitters5 is mounted on a first surface 11 a of each of the tabs 11 t of theflexible circuit board 11.

The fixture 1 also includes a heat sink member 13. The heat sink member13 is constructed of a material with good heat conduction properties andsufficient strength to support the flexible circuit board and associatedLED light emitters, typically a metal such as aluminum. Although notshown, cooling fins may be coupled to the heat sink member 13.

As noted earlier, a fixture of the type under consideration here mayinclude only one solid state emitter. In such a case, the flexiblecircuit board may have only one tab supporting the one emitter.Alternatively, the board may have more tabs, either supporting otherelements, such as one or more sensors, or provide spacers for properalignment of the board and heat sink member in relation to the lighttransmissive solid. Since we are mainly discussing examples having somenumber of (plural) emitters, each illustrated example also includes anumber of flexible tabs.

The heat sink member 13 has an inner peripheral portion of substantiallysimilar shape and of a size slightly larger than the outer peripheralportion 6 p of the light transmissive structure 6, in this case, acircular inner peripheral portion. Hence, in the example of FIGS. 1 to4, the heat sink member 13 is essentially a ring configured to surroundthe light transmissive structure 6. The inner periphery of the heat sinkmember 13, e.g. at inner edge 13 e and/or surface 13 s, corresponds inshape to the shape of the outer periphery 6 p of the light transmissivestructure 6. The outer periphery of the heat sink member 13 may have anyconvenient shape, although in the example, it is essentially circularwith a number of eyelets for screws or other fasteners to mount thefixture (see FIG. 4).

The ring shaped heat sink member 13 in the example is a single solidmember. Those skilled in the art will realize that other configurationsmay be used. For example, there may be a cut on one side of the ring anda tightening member (e.g. screw or bolt) attached through extensions orshoulders on either side of the cut to provide adjustment or tighteningof the ring shaped heat sink member 13 around the outer periphery of thehemispherical light transmissive structure 6. Another approach would beto utilize a two or three piece arrangement of the heat sink member 13with fasteners to couple the pieces of the member to form the ringaround the outer periphery of the hemispherical light transmissivestructure 6. A variety of shapes/contours may be used for the heat sinkmember instead of the relatively flat or planar ring shown and discussedby way of example here.

As assembled to form the light fixture 1, the planar mounting section 11p of the flexible circuit board 11 is mounted on an attachment surface13 p of the heat sink member 13 having an inner edge 13 e (correspondingto junction between surfaces 13 s and 13 p) at the inner peripheralportion of the heat sink member 13. The attachment surface 13 p of theheat sink member 13 is substantially planar (and is therefore referredto as a “planar” surface), for convenience in this example. The planarmounting section 11 p of the flexible circuit board 11 may be attachedto the planar attachment surface 13 p of the heat sink member 13 by anadhesive or glue or by any other cost-effective means. As describedherein substantially planar surfaces or regions, such as “planar”surfaces 13 p and/or 13 s and the “planar” region 11 p of the flexiblecircuit board 11, need not be perfectly flat but may be somewhatcontoured, curved and/or textured. Also, although surfaces and/orsections such as 13 p and 13 s and 11 p and 11 t are shown at rightangles, these angles are not critical, and the elements may beconstructed at somewhat different angles as may be convenient for usewith a transmissive structure 6 of a particular shape and/or tofacilitate easy or efficient assembly of the light fixture 1.

The flexible tabs 11 t are bent at a substantial angle with respect tothe planar mounting section 11 p, around the inner edge 13 e of thesurface 13 p of the heat sink 13, by pressure of the solid stateemitters 5 mounted on the tabs 11 t against the outer peripheral portion6 p along the contoured surface 6 c of the light transmissive structure6. In the example of FIGS. 3 and 4, the tabs bend to form curved regions11 c around the edge 13 e. A second surface 11 b of each respective oneof the tabs, opposite the first surface 11 a of the respective tab,provides heat transfer to the heat sink member, to permit heat transferfrom each solid state emitter on each respective tab to the heat sinkmember.

In the example of FIGS. 1 to 4, the fixture 1 also includes thermalinterface material (TIM) 12 positioned between the second surface 11 bof each tab 11 t and a corresponding inner surface 13 s of the heat sinkmember 13. The TIM 12 provides electrical insulation between the tabs 11t and the heat sink member 13, for example, for an implementation inwhich the heat slug of the emitter 5 is conductive. The TIM 12, however,also provides thermal conductivity to the heat sink member 13. In theexamples, pressure created by contact of the solid state light emitters5 with the outer peripheral portion 6 p of the light transmissivestructure 6 compresses the TIM 12 against the surface 13 s of the heatsink member 13.

Any of a variety of different techniques may be used to facilitate heattransfer from the emitter(s) 5 on a respective tab around, over orthrough the tab to the heat sink member 13. In the example of the lightfixture 1, there are one or more vias formed through each respective tab11 t, from the first surface 11 a of the respective tab to the secondsurface 11 b of the respective tab 11 t (FIG. 3). Heat conductivematerial 22 may extend through each via from the first surface 11 a ofthe respective tab 11 t to the second surface 11 b of the respectivetab, to conduct heat from each solid state emitter 5 on the respectivetab 11 t. In a typical implementation, heat conductive pads 21 and 23are also formed on the first and second surfaces 11 a and 11 b of eachtab 11 t. The heat conductive pad 21 on the first surface 11 a contactsthe heat slug of the emitter 5 on the respective tab 11 t. The heatconductive pad 23 on the second surface 11 b contacts the surface 13 sof the heat sink member 13. The heat conductive material 22 extendingthrough the vias through the tab 11 t conducts heat from each solidstate emitter on the respective tab 11 t, from the first pad 21 on therespective tab to the second pad 23 on the respective tab for transferto the heat sink member 13, in this case, through the compressed TIM 12.

When assembled to form the light fixture 1, the angle between the tabend 11 t holding the light emitter 5 with respect to the planar mountingsection 11 p of the flexible circuit board in the example roughlyapproaches a right angle. However, this angle is somewhat arbitrary.Different angles will be used in actual fixtures, particularly fordifferent shapes of the structure 6 and/or the heat sink member 13. Theangle may be somewhat acute or somewhat obtuse but is sufficient for thetabs 11 t to appropriately position and hold the solid state lightemitters 5 against the outer peripheral portion 6 p along the contouredsurface 6 c of the light transmissive structure 6. The positioning ofeach emitter 5 provides an orientation in which a central axis ofemission of the respective light emitter (shown as an arrow from eachLED (L) in FIG. 1) is at a substantial angle with respect to theperpendicular axis of the aperture 4 and/or the aperture surface 10 ofthe light transmissive structure 6.

The angle of emission with respect to the aperture axis may beapproximately perpendicular (90°) as in the example, although obtuse oracute angles may be used. For example, with appropriate contours for thesolid 6 and the heat sink member 13, it may be possible to aim theemitters 5 more toward the back of the reflector 3 (upward in theillustrated orientation), and the angle of direct emissions with respectto the illustrated axis might approach 45°. The intent, however, is forrelatively little of the direct emissions to impact the optical aperturesurface 10 at a steep angle. At least in the region 4 forming the actualaperture, those direct light emissions that impact the surface 10 impactat a relatively shallow angle. The ambient environment outside thefixture 1, e.g. air or water at the aperture surface 10, exhibits a lowindex of refraction. As a result, the light transmissive solid 6 has anindex of refraction higher than the ambient environment. Hence, at leastthe portion 4 of the aperture surface 10 of the light transmissive solid6 that serves as the optical aperture or passage out of the opticalintegrating volume 2 tends to exhibit total internal reflection withrespect to light reaching that surface from within the transmissivesolid 6 at relatively small angles of incidence with respect to thatsurface.

Light emitted at a low angle from any source 5 impacts the portion 4 ofthe aperture surface 10, and total internal reflection at that portionof the surface reflects the light back into the optical integratingvolume 2. In contrast, light that has been diffusely reflected fromregions of the surface 3 s of the reflector arriving at larger angles tothe surface 10 are not subject to total internal reflection and passthrough portion 4 of the aperture surface 10 of the light transmissivesolid 6.

The mask 9 therefore can be relatively small in that it only needs toextend far enough out covering the aperture surface 10 of the lighttransmissive solid 6 so as to reflect those direct emissions of thesolid state light emitters 5 that would otherwise impact the surface 10at too high or large an angle for total internal reflection. In thisway, the combination of total internal reflection in the portion 4 ofthe surface 10 of the solid 6 together with the reflective mask 9reflects all or at least substantially all of the direct emissions fromthe emitters 5, that otherwise would miss the reflector surface 3 s,back into the optical integrating volume 2. Stated another way, a personin the area or region illuminated by the fixture 1 would not perceivethe LEDs at 5 as visible individual light sources. Instead, all lightfrom the LED type emitters 5 will diffusely reflect one or more timesfrom the surface 3 s before emergence through the portion 4 of theemission surface 10 of the solid 6. Since the surface 3 s providesdiffuse reflectivity, the volume 2 acts as an optical integrating cavityso that the portion 4 of the surface 10 forms an optical apertureproviding a substantially uniform output distribution of integratedlight (e.g. substantially Lambertian).

Hence, it is possible to utilize the total internal reflection to reducethe size of the mask 9 or otherwise enlarge the effective aperture (sizeof the optical passage) at 4 through which light emerges from theintegrating volume 2. Due to the larger optical aperture or passage, thefixture 1 can actually emit more light with fewer average reflectionswithin the integrating volume 2, improving efficiency of the fixture incomparison to prior fixtures that utilized cavities and apertures thatwere open to air. It may actually be possible to diffuse the light atthe points where the LEDs 5 couple to the transmissive structure 6, e.g.by providing air gaps and/or surface texturing, to eliminate the mask 9entirely. In this later arrangement, the total internal reflection atsurface 10 serves as a virtual mask, to facilitate the desiredreflections and optical integration within the volume 2.

In the example, the reflective surface 3 s and the combination of thereflective interior surface of the mask 9 and the total internalreflection along at least region 4 of the aperture surface 10 define theboundaries of the optical integrating volume 2. As noted, the solidtransmissive structure 6 and the reflector 3 may be shaped so that theoptical integrating cavity formed by the optical volume 2 may have anyone of a variety of different shapes. For purposes of the discussion ofthe first example, however, the resulting optical integrating volume 2is assumed to be hemispherical and the aperture 4 is circular.

The effective optical aperture at 4 forms a virtual source of the lightfrom lighting apparatus or fixture 1. Essentially, electromagneticenergy, typically in the form of light energy from the one or more solidstate emitters 5, is diffusely reflected and integrated within thevolume 2 as outlined above. This integration forms combined light for avirtual source at the output of the volume, that is to say at theeffective optical aperture at 4. The integration, for example, maycombine light from multiple sources or spread light from one smallsource across the broader area of the effective aperture at 4. Theintegration tends to form a relatively Lambertian distribution acrossthe virtual source. When the fixture illumination is viewed from thearea illuminated by the combined light, the virtual source at 4 appearsto have substantially infinite depth of the integrated light. Also, thevisible intensity is spread uniformly across the virtual source, asopposed to one or more individual small point sources of higherintensity as would be seen if the one or more solid state sources weredirectly observable without sufficient diffuse processing beforeemission through an aperture.

Pixelation and color striation are problems with many prior solid statelighting devices. When a non-cavity type LED fixture output is observed,the light output from individual LEDs or the like appear asidentifiable/individual point sources or ‘pixels.’ Even with diffusersor other forms of common mixing, the pixels of the sources are apparent.The observable output of such a prior system exhibits a highmaximum-to-minimum intensity ratio. In systems using multiple lightcolor sources, e.g. RGB LEDs, unless observed from a substantialdistance from the fixture, the light from the fixture often exhibitsstriations or separation bands of different colors.

In systems and light fixtures as disclosed herein, however, opticalintegrating volume 2 converts the point source output(s) of the one ormore solid state light emitting elements 5 to a virtual source output oflight, at the effective optical aperture formed at region 4, which isfree of pixilation or striations. The virtual source output isunpixelated and relatively uniform across the apparent output area ofthe fixture, e.g. across the portion 4 of the aperture surface 10 of thesolid transmissive structure 6 in this first example (FIG. 4). Theoptical integration sufficiently mixes the light from the solid statelight emitting elements 5 that the combined light output of the virtualsource is at least substantially Lambertian in distribution across theoptical output area of the cavity, that is to say across the effectiveoptical aperture at 4. As a result, the light output exhibits arelatively low maximum-to-minimum intensity ratio across that region 4.In virtual source examples discussed herein, the virtual source lightoutput exhibits a maximum-to-minimum ratio of 2 to 1 or less oversubstantially the entire optical output area. The area of the virtualsource is at least one order of magnitude larger than the area of thepoint source output(s) of the solid state light emitter(s) 5.

In this way, the diffuse optical processing may convert a single smallarea (point) source of light from a solid state emitter 5 to a broaderarea virtual source at the region 4. The diffuse optical processing canalso combine a number of such point source outputs to form one virtualsource at the region 4.

The optical aperture 4 at the surface 10 of the solid type lighttransmissive structure 6 may serve as the light output if the fixture 1,directing optically integrated light of relatively uniform intensitydistribution to a desired area or region to be illuminated in accordwith a particular general lighting application of the fixture. In suchan arrangement, the fixture may include a trim ring or the like (notshown) covering some or all of the exposed components shown in FIG. 4(but not the aperture 4).

It is also contemplated that the fixture 1 may include one or moreadditional processing elements coupled to the effective optical aperture4, such as a colliminator, a grate, lens or diffuser (e.g. a holographicelement). In some examples, the fixture 1 may include a further opticalprocessing element in the form of a deflector or concentrator coupled tothe optical aperture 4, to distribute and/or limit the light output to adesired field of illumination. For further discussion of various typesof additional optical processing elements or ‘secondary optics’ that maybe used at or coupled to the aperture, attention may be directed to U.S.Patent Application Publications 2007/0138978, 2007/0051883 and2007/0045524, for example.

As noted earlier, the drawings presented here as FIGS. 1 to 4 aresomewhat stylized representations of a light fixture 1 utilizing a solidlight transmissive structure 6, a flexible circuit board 11 and a heatsink member 13, which are useful in illustrating and teaching thetechnologies under consideration here. FIGS. 5 to 18 are various viewsof an actual fixture and components thereof implemented in accord withsuch teachings, and like reference numerals indicate substantially thesame elements of that fixture as indicated in FIGS. 1 to 4 and discussedabove. In view of these similarities, detailed discussion of the fixtureof FIGS. 5 to 18 is omitted here. However, it may be helpful to considera few supplemental points regarding the later fixture implementationillustrated by FIGS. 5 to 18.

For example, FIG. 11 is a plan view and FIG. 12 is a side view of theflexible circuit board 11, with LEDs 5 attached to the tabs 11 t. Inthis example, there are 18 tabs and 18 LEDs. Before assembly, as shownin these two drawings, the tabs 11 t are in a flat state, substantiallyco-planar with each other and with the rest of the flexible circuitboard 11. FIG. 13 is a plan view and FIG. 14 is a side view of theflexible circuit board 11, in a state in which the tabs 11 t are bent asif the board were installed around the light transmissive structure(although the structure is omitted here for ease of illustration).

A fixture of the type outlined above will typically form part of alighting system, which includes circuitry for driving the solid statelight emitters to generate light (an example of which is discussed laterwith regard to FIG. 35). In the example of FIGS. 5 to 18, the flexiblecircuit board 11 includes a strip extending away from the mountingsection 11 p of the flexible circuit board (see e.g. FIGS. 11 and 12).The strip provides the electrical connections to other elements of thecircuitry. In such an implementation, the heat sink member 13 mayinclude a passage, for example in an extension of the member 13, asshown in drawing figures such as FIGS. 15 and 18. The strip of theflexible circuit board can be bent with respect to the mounting sectionof the flexible circuit board (see e.g. FIGS. 13 and 14), to enable thestrip to pass through the passage of the heat sink member (see e.g.FIGS. 6 and 8) to connect to the circuitry.

The present discussion encompasses a variety of different structuralconfigurations for the light transmissive structure. In the examplesshown and described above, the light transmissive structure comprises asingle light transmissive solid 6 substantially filling the volume thatforms the optical cavity. A variety of other arrangements orconfigurations may be used to construct the light transmissivestructure. As noted earlier, for example, materials containing phosphorsmay be provided within or around the solid. It may be helpful toconsider an example or two.

FIG. 19 is a cross-sectional view of an alternative construction of thelight transmissive structure, here identified by number 6′. The lighttransmissive structure 6′ is formed of two pieces 61 and 62, of lighttransmissive solid material. The material should be highly transmissiveand exhibit low absorption with respect to the relevant lightwavelengths, as discussed with regard to the example of FIGS. 1 to 4.Although other materials could be used, in this example, the two pieces61 and 62 of the light transmissive structure 6′ are formed of anappropriate glass. External properties of the structure 6′ will besimilar to those of the structure 6 in the earlier examples. Forexample, the contoured surface 6 c, at least in regions where there isno contact to a solid state light emitter, may have a roughened oretched texture.

Opposing surfaces of the two pieces 61 and 62 of the light transmissivestructure 6′ are contoured, to mate with each other around the peripheryof the junction between the pieces but form a gap 63 between the twosurfaces. The two pieces 61 and 62 of the light transmissive structure6′ may be shaped to provide the gap 63 at various locations and/or tohave various shapes. For discussion purposes, the drawing shows the gapsubstantially parallel to the aperture surface 10 at a level spaced fromthat surface 10, and extending across a substantial portion but not allof the hemispherical structure at that level. The gap 63 contains aphosphor or phosphor bearing material. There may be some additionalspace in the gap, but in the exemplary structure 6′, the phosphorbearing material at least substantially fills the volume of the gap 63.

In an example utilizing a phosphor, it is desirable to encapsulate thephosphor material in a manner that blocks out oxygen. Hence, in theexample of FIG. 19, the two solid pieces or sections 61, 62 of the lighttransmissive structure 6′ are both glass. As in the earlier example, theglass used is at least a BK7 grade or optical quality of glass, orequivalent. It is desirable for the solid, in this case the glass, tohave a high transmissivity with respect to light of the relevantwavelengths processed within the cavity 2 and/or a low level of lightabsorption with respect to light of such wavelengths. Various sealingarrangements may be provided around the edges of the chamber formed bythe gap 63, to maintain a good oxygen barrier to shield the phosphorsfrom oxygen, which degrades the phosphors reducing the useful life ofthe phosphors.

A variety of conventional phosphors may be used. Recently developedquantum dot (Q-dot) phosphors or doped quantum dot (D-dot) phosphors maybe used. Phosphors absorb excitation energy then re-emit the energy asradiation of a different wavelength than the initial excitation energy.For example, some phosphors produce a down-conversion referred to as a“Stokes shift,” in which the emitted radiation has less quantum energyand thus a longer wavelength. Other phosphors produce an up-conversionor “Anti-Stokes shift,” in which the emitted radiation has greaterquantum energy and thus a shorter wavelength. Quantum dots (Q-dots)provide similar shifts in wavelengths of light. Quantum dots are nanoscale semiconductor particles, typically crystalline in nature, whichabsorb light of one wavelength and re-emit light at a differentwavelength, much like conventional phosphors. However, unlikeconventional phosphors, optical properties of the quantum dots can bemore easily tailored, for example, as a function of the size of thedots. In this way, for example, it is possible to adjust the absorptionspectrum and/or the emission spectrum of the quantum dots by controllingcrystal formation during the manufacturing process so as to change thesize of the quantum dots. Thus, quantum dots of the same material, butwith different sizes, can absorb and/or emit light of different colors.For at least some exemplary quantum dot materials, the larger the dots,the redder the spectrum of re-emitted light; whereas smaller dotsproduce a bluer spectrum of re-emitted light. Doped quantum dot (D-dot)phosphors are similar to quantum dots but are also doped in a mannersimilar to doping of a semiconductor.

The phosphors may be provided in the gap 63 in the form of an ink orpaint applied to one or both of the mating surfaces of the pieces 61 and62. However, in the example of FIG. 19, the phosphors in the gap 63 arecarried in a binder or other medium. The medium preferably is highlytransparent (high transmissivity and/or low absorption to light of therelevant wavelengths). Although alcohol, vegetable oil or other mediamay be used, in the example of FIG. 19, the medium may be a siliconmaterial. If silicone is used, it may be in gel form or cured into ahardened form in the finished light fixture product. An example of asuitable material, having D-dot type phosphors in a silicone medium, isavailable from NN Labs of Fayetteville, Ark. A Q-Dot product, applicableas an ink or paint, is available from QD Vision of Watertown Mass.

As noted, the present discussion encompasses a variety of differentstructural configurations for the light transmissive structure. Asanother approach (FIG. 20), instead of using a solid structure (e.g.FIG. 1) or solid structure with a gap or chamber for a phosphor (FIG.19), the light transmissive structure may comprise a container. Althoughthe container could be filled with a gas, in the illustrated example,the container is filled with a liquid. The liquid may contain aphosphor, such as one or more of the Q-dot or D-dot phosphors mentionedabove. FIG. 20 is an example of a light transmissive structure 6″constructed in such a manner.

As shown in FIG. 20, the light transmissive structure 6″ includes acontainer. Although other container structures may be used, for ease ofillustration, the exemplary container is formed of a plate 64 and ahemispherical dome 65. As in the solid examples, these elements shouldexhibit high transmissivity and low absorption with respect to light ofthe relevant wavelengths. Although other materials could be used, toprovide good containment and an excellent oxygen barrier, the example ofFIG. 20 uses glass for the plate 64 and the dome 65.

In the example of FIG. 20, the container formed by the plate 64 and thedome 65 is filled with a liquid 66. The liquid could be transparent ortranslucent, with no active optical properties. However, for discussionpurposes, the liquid 66 contains phosphor materials, such as Q-dot orD-dot quantum type nano phosphors. Those skilled in the art willrecognize that there are various ways to join the components of thecontainer, such as 64 and 65, together to form a liquid tight and airtight seal, and that there are various ways to fill the container withthe desired liquid in a manner that eliminates at least substantiallyall oxygen bearing gases. In the illustrated example, the liquid 66substantially fills the volume of the container formed by the elements64 and 65, with little or no gas entrained in the liquid 66.

The phosphors contained in the gap 63 or in the liquid 66 will beselected to facilitate a particular lighting application for theparticular fixture. That is to say, for a given spectrum of lightproduced by the LEDs (L) and the diffusely reflective optical cavity,the material and/or sizing of the nano phosphors or other phosphors willbe such as to shift at least some of the light emerging through theaperture in a desired manner.

Nano phosphors are often produced in solution. Near the final productionstage, the nano phosphors are contained in a liquid solvent. In a nanophosphor example, this liquid solution could be used as the solution 66in the example of FIG. 20. However, the solvents tend to be rathervolatile/flammable, and other liquids such as water or vegetable oil maybe used. The phosphors may be contained in a dissolved state insolution, or the liquid and phosphors may form an emulsion. The liquiditself may be transparent, or the liquid may have a scattering ordiffusing effect of its own (caused by an additional scattering agent inthe liquid or by the translucent nature of the particular liquid).

The container formed by the plate 64 and the dome 65, together with theliquid 66, substantially fill the optical volume 2, of the light fixturethat incorporates the structure 6″. External properties of the structure6″ will be similar to those of the structure 6 in the earlier examples.For example, the contoured surface 6 c, at least in regions where thereis no contact to a solid state light emitter, may have a roughened oretched texture.

FIG. 21 is a cross-sectional view of yet another alternativeconstruction of the light transmissive structure, here identified bynumber 6′, which incorporates a phosphor or phosphor bearing material69. For example, the structure may utilize two pieces of the lighttransmissive solid with a gap therebetween, filled with the phosphor orphosphor bearing material, similar to the structure of FIG. 19. However,rather than positioning the phosphor somewhat near the middle of thevolume of the light transmissive structure as in FIG. 19, thearrangement of FIG. 21 locates the phosphor near or at the opticalaperture surface of the light transmissive structure.

In the example of FIG. 21, the light transmissive structure 6″′comprises a main section 67, which is essentially similar to the solid 6the example of FIG. 1. However, the light transmissive structure 6′″also includes a section 68 containing the phosphor and forming theaperture surface 10. The section 68 may be constructed in a number ofdifferent ways, two examples of which are represented by the enlargeddetail sections (corresponding approximately to the region encircled atB-B in FIG. 21) of FIGS. 21A and 21B.

For example, the pieces of the light transmissive solid with a gaptherebetween may consist of the main section 67 and an additional lighttransmissive member 681 (FIG. 21A). In such an arrangement, the phosphorcontainment section 68 a includes the member 681 and the gap formedbetween that member and the face of the main section 67. The gap isfilled with a phosphor or phosphor bearing material, such as discussedabove relative to the example of FIG. 19. The member 681 is attached tothe section 67 in a manner to provide an air tight seal. In such anarrangement, the main section 67 and the light transmissive member 681would typically be formed of glass, to insure that no air reaches thephosphor contained in the gap.

In the other example (FIG. 21B), the phosphor containment section 68 bincludes two pieces of the light transmissive solid members 682 and 683with a gap therebetween, filled with a phosphor or phosphor bearingmaterial 69. In this arrangement, the solid element 682 is attached toor positioned against/adjacent to the face of the main section 67. Thetwo light transmissive solid members 682 and 683 typically would beglass and would be sealed to contain the phosphor in an air tightmanner. However, with this arrangement, it may be feasible to use adifferent light transmissive material for the main section 67, as thatsection need not be impervious to gas leakage.

As in the earlier examples, it may be desirable to provide a roughenedor etched texture at the optical aperture, for example, on the surface10 of the appropriate element or section in any of the examples of FIGS.19-21. In the versions using a phosphor, the texture at the aperture mayhelp to obscure the non-white coloration of the phosphor bearingmaterial when the light fixture is not turned ON.

FIG. 22 is a cross-section of another example of a light fixture orengine 71 intended for general lighting, for example, in a region orarea intended to be occupied by a person. FIG. 23 is a cross-sectionalview of a one-piece solid construction of the light transmissivestructure 76 that forms the optical volume 72, in the fixture or engine71 of FIG. 22. FIGS. 24-29 provide other views of the fixture or engine71. These and other drawings of this example are not drawn to scale. Inseveral of the illustrations, such as FIGS. 22 and 29, for convenience,the lighting apparatus is shown in an orientation for emitting lightdownward. However, the apparatus 71 may be oriented in any desireddirection to perform a desired general lighting application function.

The apparatus 71 could be used alone to form a light fixture or morelikely would be used with other housing elements and possibly with asecondary optic (e.g. such as shown in FIG. 34) to form the overallcommercial light fixture product. Together with the other electricalcomponents (e.g. as in FIG. 35), the apparatus or “light engine” 71 ofFIG. 22 or the fixture of FIG. 35 would form a lighting system.

The exemplary fixture or engine 71 includes a plurality of LED typesolid state light emitters 75 and a light transmissive structure 76forming a volume 72. As in the earlier examples, the emitters 75 aresufficient in number and strength of output for the light engine 71 toproduce light intensity sufficient for the general lighting applicationof the fixture.

As shown in FIG. 23, the light transmissive structure 76 has a contouredouter surface 76 c and an optical aperture surface 80. In this example,the surface 76 c corresponds to a segment of a sphere somewhat less thana hemisphere and does not extend continuously to the periphery of theaperture surface 80 as in the earlier examples. In this example, thelight transmissive structure 76 also has a peripheral optical couplingsurface 76 p between the contoured outer surface 76 c and the opticalaperture surface 80. In this example, the peripheral optical couplingsurface 76 p forms an obtuse angle with respect to the optical aperturesurface 80 (and an acute angle with respect to the vertical in thedownlight orientation of FIG. 22). At least the outer peripheral portion76 p of the structure 76 along the lower portion of contoured surface 76c is substantially rigid.

In this example, the contoured surface 76 c has a roughened or etchedtexture, and some or all of the aperture surface 80 may have a roughenedor etched texture. In such an implementation, at least any portion ofthe angled peripheral optical coupling surface 76 p of the lighttransmissive structure 76 that receives light from one of the solidstate light emitters 75 likely would be highly transparent. Of course,the aperture surface 80 may be highly transparent as well. In theexample, the aperture surface 80 is shown as a flat surface. However,those skilled in the art will recognize that this surface 80 may have aconvex or concave contour.

In the example of FIGS. 22-29, the outer surfaces of the structure 76approach or approximate a hemisphere that is somewhat truncated at theperipheral region by the angled surface 76 p. Again, the opticalaperture surface now indentified by number 80 approximates a circle.Examples having shapes corresponding to a portion or segment of a sphereor cylinder are preferred for ease of illustration and/or because curvedsurfaces provide better efficiencies than other shapes that include moreedges and corners which tend to trap light. Those skilled in the artwill understand, however, that the volume of the light transmissivestructure, and thus the optical cavity 72 of the fixture or light engine71, may have any shape providing adequate reflections within thevolume/cavity for a particular application. For example, the contour ofthe upper surface 76 c may be hemispherical, may correspond in crosssection to a segment of a circle less than a half circle (less thanhemispherical), or may extend somewhat further than a hemisphere tocorrespond in cross section to a segment of a circle larger than a halfcircle. Also, the contoured portion 76 c may be somewhat flattened orsomewhat elongated relative to the illustrated axis of the aperture 74,the aperture surface 80 and the exemplary solid 76 (in the verticaldirection in the exemplary downlight orientation depicted in FIG. 22).The coupling surface 76 p is shown having a substantially flatcross-section, although of course it would curve around the circularstructure 76. However, other shapes or contours for the surface 76 p maybe used, for example, with a convex cross section or concavecross-section or with indentations to receive emitting surfaces orelements of particular types of LEDs 75.

In a manner similar to the examples of FIGS. 1-10, in the example ofFIGS. 22 and 23 the light transmissive structure forming the volume 72comprises a one piece light transmissive solid 76 substantially fillingthe volume 72. Materials containing phosphors may be provided within oraround the solid, as discussed earlier, although for simplicity,phosphors and containment thereof are omitted from the example shown inFIGS. 22 and 23. The solid 76 is a single integral piece of lighttransmissive material. The material, for example, may be a highlytransmissve and/or low absorption acrylic having the desired shape. Inthis example, the light transmissive solid structure 76 is formed of anappropriate glass, such as a fused silica type glass of at least a BK7grade or equivalent optical quality. For optical efficiency, it isdesirable for the solid structure 76, in this case the glass, to have ahigh transmissivity with respect to light of the relevant wavelengthsprocessed within the optical cavity 72 and/or a low level of lightabsorption with respect to light of such wavelengths. For example, in animplementation using BK7 or better optical quality of glass, the highlytransmissive glass exhibits 0.99 internal transmittance or better (BK7exhibits a 0.992 internal transmittance).

The fixture or light engine 71 also includes a reflector 73, which has adiffusely reflective interior surface 73 s extending over at least asubstantial portion of the outer surface of the light transmissivestructure 76, in this case over the contoured outer surface 76 calthough it could extend over some portion or portions of the angledcoupling surface 76 p not expected to receive light input from theemitters 75. The surface 76 c is roughened for example by etching. Foroptical efficiency, however, the surface texture should provide only aminimal air gap between the diffusely reflective interior surface 73 sof the reflector 73 and the corresponding portion(s) of the contouredouter surface 76 c of the light transmissive structure 76. The diffusereflective surface 73 s forms an optical cavity from and/or encompassingthe volume 72 of the light transmissive structure 76, with an opticalaperture 74 formed from a portion or all of the aperture surface 80 ofthe light transmissive structure 76.

It is desirable that the diffusely reflective surface(s) 73 s of thereflector 73 have a highly efficient reflective characteristic, e.g. areflectivity equal to or greater than 90%, with respect to the relevantwavelengths. Diffuse white materials exhibiting 98% or greaterreflectivity are available. Although other materials may be used,including some discussed above relative to earlier examples, theillustrated example of FIG. 22 uses WhiteOptics™. The WhiteOptics™reflector 73 is approximately 97% reflective with respect to the visiblewhite light from the LED type solid state emitters 75. In the example,the entire inner surface 73 s of the reflector 73 is diffuselyreflective, although those skilled in the art will appreciated that oneor more substantial portions may be diffusely reflective while otherportion(s) of the surface 73 s may have different light reflectivecharacteristics, such as a specular or semi-specular characteristic.

At least a portion of the aperture surface 80 of the light transmissivestructure 76 serves as a transmissive optical passage or effective“optical aperture” 74 for emission of integrated light, from the opticalintegrating volume 72, in a direction to facilitate the particulargeneral lighting application in the region or area to be illuminated bythe light fixture (generally downward and/or outward from the fixture inthe orientation of FIG. 22). The entire surface 80 of the solidstructure 76 could provide light emission. However, the example of FIG.22 includes a mask 79 having a reflective surface facing into theoptical integrating volume 72, which somewhat reduces the surface areaforming the transmissive passage to that portion of the surface shown at74. The optical volume 72 operates as an optical integrating cavity(albeit one filled with the light transmissive solid of structure 76),and the passage 74 for light emission forms the optical aperture of thatcavity.

As noted, the surface of the mask 79 that faces into the opticalintegrating volume 72 (faces upward in the illustrated orientation) isreflective. That surface may be diffusely reflective, much like thesurface 73 s, or that mask surface may be specular, quasi specular orsemi-specular. Other surfaces of the mask 79 may or may not bereflective, and if reflective, may exhibit the same or differenttypes/qualities of reflectivity than the surface of the mask 79 thatfaces into the optical integrating volume 72. In one configuration, thesurface of the mask 79 that faces into the optical integrating volume 72might be diffusely reflective (having reflective properties similar tothose of reflective surface 73 s), whereas the surface of the maskfacing inward/across the aperture 74 might be specular. Specularreflectivity across the aperture reduces reflection back through theaperture into the integrating volume due to diffuse reflection thatmight otherwise occur if that portion of the mask exhibited a diffusereflectivity.

In the example, the light fixture 71 also includes one or more solidstate light emitters 75. An emitter 75 may be any appropriate type oflight emitting semiconductor based device. In the specific examplesdiscussed herein the solid state light emitters are light emittingdiodes (LEDs). The present teachings encompass use of varioustypes/colors of LEDs, such as red (R), green (G) and blue (B) LEDs,ultraviolet (LEDs) to pump phosphors in the fixture, LEDs of two or moredifferent color temperatures of white light, etc. Various combinationsof different colors of LEDs may be used. However, for simplicity, thediscussion of this example will assume that the LED type solid statelight emitters 75 are white light LEDs rated to all emit the same colortemperature of white light. Hence, in the illustrated example of thecircuitry (FIG. 35 as discussed, later), each LED is a white LED of thesame or similar model. As noted, there may be as few as one solid stateemitter, however, for illustration and discussion purposes, we willassume in most instances below that the fixture includes a plurality ofsolid state emitters. The number and output capabilities of the solidstate light emitters 75 are such that the combined white light outputvia the aperture 74 provides light intensity sufficient for a particulargeneral lighting application intended for the light fixture 71. Anactual downlight implementations, for example, might include fifteenwhite LEDs as the solid state light emitters 75.

As discussed more below, the light emitters 75 are held against theangled peripheral optical coupling surface 76 p, to supply light throughthat surface into the interior volume 72 formed by the lighttransmissible structure 76. There may be some minimal air gap betweenthe emitter output and the optical coupling surface 76 p. However, toimprove out-coupling of light from the emitters 75 into the lighttransmissive solid structure 76, it may be helpful to provide an opticalgrease, glue or gel between the peripheral optical coupling surface 76 pand the output of each solid state light emitter 75. This materialeliminates any air gap and provides refractive index matching relativeto the material of the relevant portion of the light transmissivestructure 76, for example, the material forming the angled peripheraloptical coupling surface 76 p.

The exemplary light fixture or engine 71 also includes a flexiblecircuit board 81. In a manner similar to the earlier examples in FIGS. 3and 11-14, the flexible circuit board 81 has a mounting section orregion 81 p that typically will be at least substantially planar (and istherefore referred to herein as a “planar” mounting section) forconvenience in this example. The planar mounting section 81 p of theflexible circuit board 81 has an inner peripheral portion 11 i. In thisexample, the lateral shape of the solid forming the light transmissivestructure 76 is circular (see e.g. top view in FIG. 26). The innerperipheral portion of the flexible circuit board 81 has a shapesubstantially similar shape, that is to say a circular shape in theexample. The circular inner peripheral portion of the flexible circuitboard 81 has a size slightly larger than the circular outer peripheralportion at the edge between the surfaces 76 c and 76 p of the lighttransmissive structure 76. The flexible circuit board includes a strip81 e, extending away from the planar mounting section, for providingelectrical connection(s) to the driver circuitry.

The flexible circuit board 81 also has flexible tabs 81 t attached toand extending from the inner peripheral region of the flexible circuitboard 81. As noted earlier, the number and type of LED type solid statelight emitters 75 used in the fixture 71 are selected so as to producelight intensity sufficient for a general lighting application of thefixture 71. The emitters 75 are mounted on the tabs 81 t. At least oneof the solid state light emitters 75 is mounted on a first surface ofeach of the tabs 81 t of the flexible circuit board 81, in this example,although some tabs could be empty or carry other elements such as alight sensor instead of an LED.

As in the earlier examples, the fixture 71 also includes a heat sinkmember 83. The heat sink member 83 is constructed of a material withgood heat conduction properties and sufficient strength to support theflexible circuit board and associated LED light emitters, typically ametal such as aluminum. As shown in a later drawing (FIG. 33), coolingfins may be coupled to the heat sink member 83, for example, as part ofone or more additional aluminum housing components. More detailed viewsof the heat sink member or ring 83 are shown in FIGS. 31-33.

The heat sink member 83 has an inner peripheral portion of substantiallysimilar shape and of a size slightly larger than the outer peripheralportion of the light transmissive structure 76. In this case, the heatsink member 83 has a circular inner peripheral portion but with asurface 91 (FIGS. 30 and 32) at a slant corresponding to the angle ofsurface 76 p. The obtuse angle of the peripheral optical couplingsurface 76 p with respect to the optical aperture surface 80 of lighttransmissive structure is approximately 120° (interior angle withrespect to the horizontal in the illustrated orientation is 60°, andangle of the surface cross section relative to the vertical in theillustrated orientation is 30°. Hence, although the inner peripheralportion of the heat sink member 83 has a somewhat larger diameter thanthe outer peripheral portion of the light transmissive structure 76, theinner surface (91 in FIG. 30) of the heat sink member 83 is machined tohave an angle of approximately 120° with respect to the optical aperturesurface 80 (interior angle with respect to the horizontal in theillustrated orientation of FIG. 22 is 60°, and angle of the surfacecross section relative to the vertical in the illustrated orientation ofFIG. 22 is 30°.

The ring shaped heat sink member 83 in the example is a single solidmember, for example, formed of aluminum. Those skilled in the art willrealize that other configurations may be used, as discussed above withregard to other examples. The opposite side of heat sink member 83 (FIG.33) may have a ring-shaped indentation 93 for mating with the mask 79(FIG. 22). The exemplary heat sink also includes one or more posts 92(FIGS. 30-33) extending outward from the main part of the ring. Eachpost 92 has a screw or bolt hole for passage of a bolt or similarfastener, for use in the assembly of the light engine 71 together withother components.

Returning to FIG. 22, as assembled to form the light fixture or engine71, the planar mounting section 81 p of the flexible circuit board 81 ismounted on an attachment surface of the heat sink member 83 having aninner edge corresponding to junction between angled inner surface andthe mounting surface. In the illustrated downlight orientation (FIG.22), attachment surface of the heat sink member is on the top side ofthe heat sink member. The mounting section of the flexible circuit board81 may be attached to the planar attachment surface of the heat sinkmember 83 by an adhesive or glue or by any other cost-effective means.

The flexible tabs 81 t are bent at a substantial angle with respect tothe mounting section of the heat sink member 81, around the inner edgeof that surface, by pressure of the solid state emitters 75 mounted onthe tabs 81 t against the outer peripheral coupling surface 76 p of thelight transmissive structure 76. In the illustrated downlightorientation (FIG. 22), each tab will bend to an angle approximately thesame as the angle of the surfaces that it fits between, in this caseapproximately 120° with respect to the optical aperture surface 80(interior angle with respect to the horizontal in the illustratedorientation of FIG. 22 is 60°, and angle of the surface cross sectionrelative to the vertical in the illustrated orientation of FIG. 22 is30°.

The tabs may be constructed in a manner similar to those in the earlierexamples. The first surface of a tab 81 t supports a solid state lightemitter 75 and receives heat from the emitter. The tab 81 t isconstructed to conduct the heat from the solid state light emitter 75 toits opposite or second surface. The second surface of each respectiveone of the tabs provides heat transfer to the heat sink member 83, topermit heat transfer from each solid state emitter on each respectivetab to the heat sink member.

In the example of FIG. 22, the fixture or light engine 71 also includesthermal interface material (TIM) 82 positioned between the secondsurface of each tab 81 t and a corresponding inner surface of the heatsink member 83. The TIM 82 provides electrical insulation between thetabs 81 t and the heat sink member 83, for example, for animplementation in which the heat slug of the emitter 75 is conductive.The TIM 82, however, also provides thermal conductivity to the heat sinkmember 83. In the examples, pressure created by contact of the solidstate light emitters 75 with the angled optical coupling surface 76 palong the outer peripheral portion of the light transmissive structure76 compresses the TIM 82 against the surface of the heat sink member 83.

The positioning of each emitter 75 provides an orientation in which acentral axis of emission of the respective light emitter (shown as anarrow from each LED in FIG. 22) is at a substantial angle with respectto the perpendicular axis of the aperture 74 and/or of the aperturesurface 80 of the light transmissive structure 76. In the earlierexamples, the angle of emission with respect to the aperture axis may beapproximately perpendicular (90°). In this example (FIG. 22), however,the coupling surface 76 p is at an angle so that the central axis ofemission of the respective light emitter 75 is directed somewhat moreaway from aperture 74 and/or the aperture surface 80 of the lighttransmissive structure 76. Since, the central axis of emission of therespective light emitter 75 is substantially perpendicular to thecoupling surface 76 p, and the coupling surface 76 p forms an obtuseangle with respect to the aperture surface 80, the central axis ofemission of the respective light emitter 75 in this example is at anacute angle away from the aperture surface 80.

Although other angles may be used, the coupling surface 76 p in theexample forms an angle of approximately 120° with respect to theaperture surface 80, therefore the angle between the central axis ofemission of the respective light emitter 75 and the aperture surface 80in this example is approximately 30°. From another perspective, thisresults in the central axis of emission of the respective light emitter75 having approximately a 60° angle with respect to the perpendicularaxis of the aperture 74 and/or of the aperture surface 80 of the lighttransmissive structure 76.

This angle of emission from the emitters 75 reduces even further theamount of the direct emissions that impact the optical aperture surface80 at a steep angle. At least in the region 74 forming the actualaperture, those direct light emissions that do impact the surface 80impact at a relatively shallow angle. Somewhat more even than in theearlier examples, the portion 74 of the aperture surface 80 of the lighttransmissive solid 76 that serves as the optical aperture or passage outof the optical integrating volume 72 exhibits total internal reflectionwith respect to light reaching that surface directly from the emitters75, and that total internal reflection reflects direct light emissionhitting the surface at a shallow angle back into the optical integratingvolume 72. In contrast, light that has been diffusely reflected fromregions of the surface 73 s of the reflector arriving at larger anglesto the surface 80 are not subject to total internal reflection and passthrough portion 74 of the aperture surface 80 that forms the opticalaperture.

The mask 79 therefore can be relatively small in that it only needs toextend far enough out covering the aperture surface 80 of the lighttransmissive solid 76 so as to block direct view of the LEDs 75 throughthe aperture 74 and to reflect those few direct emissions of the solidstate light emitters 75 that might otherwise still impact the surface 80at too high or large an angle for total internal reflection. In thisway, the combination of total internal reflection in the portion 74 ofthe surface 80 of the solid 76 together with the reflective mask 79reflects all or at least substantially all of the direct emissions fromthe emitters 75, that otherwise would miss the reflector surface 73 s,back into the optical integrating volume 72. Stated another way, aperson in the area or region illuminated by the fixture 71 would notperceive the LEDs at 75 as visible individual light sources. Instead,virtually all light input to the volume from the LED type emitters 75will diffusely reflect one or more times from the surface 73 s beforeemergence through the aperture portion 74 of the surface 80 of the solid76. Since the surface 73 s provides diffuse reflectivity, the volume 72acts as an optical integrating cavity so that the portion 74 of thesurface 80 forms an optical aperture providing a substantially uniformoutput distribution of integrated light (e.g. substantially Lambertian).

As in the earlier examples, it is possible to utilize the total internalreflection to reduce the size of the mask 79 or otherwise enlarge theeffective aperture (size of the optical passage) at 74 through whichlight emerges from the integrating volume 72. Due to the larger opticalaperture or passage, the fixture 71 can actually emit more light withfewer average reflections within the integrating volume 72, improvingefficiency of the fixture in comparison to prior fixtures that utilizedcavities and apertures that were open to air.

The effective optical aperture at 74 forms a virtual source of the lightfrom lighting apparatus or fixture 71, which exhibits a relativelyLambertian distribution across the virtual source, as in the earlierexamples. When the fixture illumination is viewed from the areailluminated by the combined light, the virtual source at 74 appears tohave substantially infinite depth of the integrated light. Also, thevisible intensity is spread uniformly across the virtual source, asopposed to one or more individual small point sources of higherintensity as would be seen if the one or more solid state sources weredirectly observable without sufficient diffuse processing beforeemission through an aperture. Again, the optical integration in thevolume 72 reduces or eliminates pixelation and color striation in thelight output via the aperture 74. The light output exhibits a relativelylow maximum-to-minimum intensity ratio across that region 74. In virtualsource examples discussed herein, the virtual source light outputexhibits a maximum to minimum ratio of 2 to 1 or less over substantiallythe entire optical output area. The area of the virtual source is atleast one order of magnitude larger than the area of the point sourceoutput(s) of the solid state light emitter(s) 75. In this way, thediffuse optical processing may convert a single small area (point)source of light from a solid state emitter 75 to a broader area virtualsource at the region 74. The diffuse optical processing can also combinea number of such point source outputs to form one virtual source at theregion 74.

As discussed earlier, the optical aperture 74 at the surface 80 of thesolid type light transmissive structure 76 may serve as the light outputif the fixture 71, directing optically integrated light of relativelyuniform intensity distribution to a desired area or region to beilluminated in accord with a particular general lighting application ofthe fixture. In such an arrangement, the fixture may include a trim ringor the like (not shown) covering some or all of the exposed components(but not the aperture 74).

However, the light engine example 71 of FIG. 22 is intended for use withother elements to form a commercial fixture. As shown in cross-sectionin FIG. 34, the commercial fixture product 90 includes the elements ofthe light engine, including the reflector 73, emitters 75, lighttransmissive structure 76 (with aperture surface 80), mask 79, heat sinkring 81, etc. The fixture 90 also includes an upper housing or cover 94and a lower housing 96. The upper housing 94 encloses the reflector 73and the solid light transmissive structure 76 although it is somewhatlarger than the reflector 73 and the solid light transmissive structure76 so that there is some space between the reflector and the innercurved surface of the upper housing 94.

The fixture 90 also includes a flexible compressible pad 95, between theinner surface of the upper housing 94 and the outer surface of thereflector 73. Although other attachment mechanisms may be used, in thisexample, the upper housing 94 is bolted to a lower hosing 96. The boltsextend through holes in posts 92 formed in the heat sink ring 81 (seee.g. FIGS. 30-33). In this way, the heat sink ring 81 is sandwichedbetween opposed surfaces of the housing members 94, 96 (FIG. 34). Theinner surface of the upper housing 94 and the pad 95 are sized so thatthe assembly of the housings and the heat sink ring compresses the pad95 between the inner surface of the upper housing 94 and the outersurface of the reflector 73. This applies pressure through the reflector73 to the solid light transmissive structure 76, to hold the structure76 as well as the LEDs 75, the tabs of the flexible circuit board andthe TIM against the angled surface of the heat sink ring 81, as shownfor example in FIGS. 22 and 34. The aperture surface 80 also abuts thewhite reflective surface of the mask 79. The use of the angled shapesalso tends to align the various components of the light engine (71 inFIG. 22) in the desired manner, for example, without tilt of thestructure 76 or surface 80 relative to the mask 79.

The housing elements 94, 96, like the heat sink ring 81, are formed of agood heat conductive material. In the example, the housings 94, 96 maybe cast aluminum elements. Outer portions of one or preferably bothhousings 94, 96 incorporate fins Heat from the emitters 75 istransferred to the heat sink ring 81, as discussed earlier. From thering 81, the heat travels to the housings 94, 96 where it may bedissipated to the surrounding atmosphere via the fins. To promote heattransfer from the heat sink member or ring 81 to the housings, thefixture may include adhesive TIM layers on the appropriate surfaces ofthe heat sink ring 81 (see FIG. 22).

The fixture 90 illustrated in FIG. 34 also includes a secondary optic.Although other secondary optics may be used, in this example thesecondary optic includes a deflector or concentrator 97 having areflective inner surface. The surface may have different reflectivecharacteristics. For example specular, semi-specular and diffusereflectivities and/or combinations thereof are contemplated. As notedabove, the surface of the mask 79 that faces into the opticalintegrating volume 72 (faces upward in the orientation illustrated inFIGS. 22 and 34) may be diffusely reflective. The mask includes a bossformed to extend away from the aperture surface 80. The inner surface ofthis boss or extension faces across the aperture opening through themask 79 and might be considered the start of the secondary optic formedby or together with the deflector 97. The inner surface of the boss orextension and the inner surface of the deflector 97 may have similarspecular reflective properties. As shown in FIG. 34, the fixture 90 mayalso include a trim ring 98 to facilitate a desired appearance when thefixture for example is mounted in a ceiling.

The solid state emitters in any of the fixtures discussed above may bedriven by any known or available circuitry that is sufficient to provideadequate power to drive the emitters at the level or levels appropriateto the particular general lighting application of each particularfixture. Analog and digital circuits for controlling operations anddriving the emitters are contemplated. Those skilled in the art shouldbe familiar with various suitable circuits. However, for completeness,we will discuss an example of suitable circuitry, with reference to FIG.35. That drawing figure is a block diagram of an exemplary solid statelighting system 100, including the control circuitry and the LED typesold state light emitters utilized as a light engine 101 in a fixture orlighting apparatus of such a system. Those skilled in the art willrecognize that the system 100 of FIG. 35 may include a number of thesolid state light engines 101. The light engine(s) 101 could beincorporated into a fixture in any of the examples discussed above, withthe LEDs shown in FIG. 35 serving as the various solid state emitters inthe exemplary fixture and the connections thereto provided via theflexible circuit board.

The circuitry of FIG. 35 provides digital programmable control of thelight. Those skilled in the art will recognize that simpler electronicsmay be used for some fixture configurations, for example, an all whiteLED fixture with little or no variability may have only a power supplyand an ON/OFF switch.

In the light engine 101 of FIG. 35, the set of solid state sources oflight takes the form of a LED array 111. A circuit similar to that ofFIG. 35 has been used in the past, for example, for RGB type lighting(see e.g. U.S. Pat. No. 6,995,355) and could be used in a similar mannerwith LEDs of two or more colors. Different LED colors could be differentprimary colors or different color temperatures of white light. For afixture that includes phosphors, the LEDs may be or include UV LEDs.However, for purposes of discussion of the main examples underconsideration here, we will assume that the LEDs of the array 111 areall white LEDs rated for the same color temperature output.

Hence, the exemplary array 111 comprises one or more LEDs arranged ineach of four different strings. Here, the array 111 includes threeinitially active strings of LEDs, represented by LED blocks 113, 115 and117. The strings may have the same number of one or more LEDs, or thestrings may have various combinations of different numbers of one ormore LEDs. For purposes of discussion, we will assume that the firstblock or string of LEDs 113 comprises 6 LEDs. The LEDs may be connectedin series, but in the example, two sets of 3 series connected LEDs areconnected in parallel to form the block or string of 6 white LEDs 113.The LEDs may be considered as a first channel C₁, for control purposes.

In a similar fashion, the second block or string of LEDs 115 comprises 8LEDs. The 8 LEDs may be connected in series, but in the example, twosets of 4 series connected LEDs are connected in parallel to form theblock or string of 8 white LEDs 115. The third block or string of LEDs117 comprises 12 LEDs. The 12 LEDs may be connected in series, but inthe example, two sets of 6 series connected LEDs are connected inparallel to form the block or string of 12 white LEDs 117. The LEDs 115may be considered as a second channel C₂, whereas the LEDs 117 may beconsidered as a third channel C₃, for control purposes.

The LED array 111 in this example also includes a number of additionalor ‘other’ LEDs 119. As noted, some implementations may include variouscolor LEDs, such as specific primary color LEDs, IR LEDs or UV LEDs, forvarious purposes. Another approach might use the LEDs 119 for a fourthchannel to control output intensity. In the example, however, theadditional LEDs 119 are ‘sleepers.’ Initially, the LEDs 113-117 would begenerally active and operate in the normal range of intensity settings,whereas sleepers 119 initially would be inactive. Inactive LEDs areactivated when needed, typically in response to feedback indicating aneed for increased output (e.g. due to decreased performance of some orall of the originally active LEDs 113-117). The set of sleepers 119 mayinclude any particular number and/or arrangement of the LEDs as deemedappropriate for a particular application.

Each string may be considered a solid state light emitting elementcoupled to supply light to the optical cavity, where each such elementor string comprises one or more light emitting diodes (LEDs) serving asindividual solid state emitters. In the example of FIG. 35, each suchelement or string 113 to 119 comprises a plurality of LEDs.

The electrical components shown in FIG. 35 also include a LED controlsystem 120 as part of the light engine 101. The system 120 includesdriver circuits 121 to 127 for the various LEDs 113 to 119, associateddigital to analog (D/A) converters 122 to 128 and a programmablemicro-control unit (MCU) 129. The driver circuits 121 to 127 supplyelectrical current to the respective LEDs 113 to 119 to cause the LEDsto emit visible light or other light energy (e.g. IR or UV). Each of thedriver circuits may be implemented by a switched power regulator (e.g.Buck converter), where the regulated output is controlled by theappropriate signal from a respective D/A converter. The driver circuit121 drives the string of LEDs 113, the driver circuit 123 drives thestring of LEDs 115, and the driver circuit 125 drives the string of LEDs117. In a similar fashion, when active, the driver circuit 127 provideselectrical current to the other LEDs 119. If the other LEDs provide asingle color of light, and are connected together, there may be a singledriver circuit 127. If the LEDs are sleepers, it may be desirable toprovide a separate driver circuit 127 for each of the LEDs 119, for eachof two or more sets of similar LEDs, or for each set of LEDs of adifferent color.

The driver circuits supply electrical current at the respective levelsfor the individual sets of LEDs 113-119 to cause the LEDs to emit light.The MCU 129 controls the LED driver circuit 121 via the D/A converter122, and the MCU 129 controls the LED driver circuit 123 via the D/Aconverter 124. Similarly, the MCU 129 controls the LED driver circuit125 via the D/A converter 126. The amount of the emitted light of agiven LED set or string is related to the level of current supplied bythe respective driver circuit, as set by the MCU 129 through therespective D/A converter. Although not shown, controlled switches may beprovided to allow the MCU to selectively activate/deactivate each of thestrings 113-119 of LEDs.

In a similar fashion, the MCU 129 controls the LED driver circuit 127via the D/A converter 128. When active, the driver circuit 127 provideselectrical current to the other LEDs 119. If the LEDs are sleepers, itmay be desirable to provide a separate driver circuit and A/D converterpair, for each of the LEDs 119 or for other sets of LEDs of theindividual primary colors.

In operation, one of the D/A converters receives a command for aparticular level, from the MCU 129. In response, the converter generatesa corresponding analog control signal, which causes the associated LEDdriver circuit to generate a corresponding power level to drive theparticular string of LEDs. The LEDs of the string in turn output lightof a corresponding intensity. The D/A converter will continue to outputthe particular analog level, to set the LED intensity in accord with thelast command from the MCU 129, until the MCU 129 issues a new command tothe particular D/A converter.

The control circuit could modulate outputs of the LEDs by modulating therespective drive signals. In the example, the intensity of the emittedlight of a given LED is proportional to the level of current supplied bythe respective driver circuit. The current output of each driver circuitis controlled by the higher level logic of the system. In this digitalcontrol example, that logic is implemented by the programmable MCU 129,although those skilled in the art will recognize that the logic couldtake other forms, such as discrete logic components, an applicationspecific integrated circuit (ASIC), etc.

The LED driver circuits and the MCU 129 receive power from a powersupply 131, which is connected to an appropriate power source (notseparately shown). For most general lighting applications, the powersource will be an AC line current source, however, some applications mayutilize DC power from a battery or the like. The power supply 131converts the voltage and current from the source to the levels needed bythe various elements of the LED control 120.

A programmable microcontroller, such as the MCU 129, typically comprisesa programmable processor and includes or has coupled theretorandom-access memory (RAM) for storing data and read-only memory (ROM)and/or electrically erasable read only memory (EEROM) for storingcontrol programming and any pre-defined operational parameters, such aspre-established routines. In a white light system, the routine mightvary overall intensity with time over some set period. In a system usingmultiple different colors of LEDs, a light ‘recipe’ or ‘routine’ mightprovide dynamic color variation. The MCU 129 itself comprises registersand other components for implementing a central processing unit (CPU)and possibly an associated arithmetic logic unit. The CPU implements theprogram to process data in the desired manner and thereby generatesdesired control outputs to cause the system to generate a virtual sourceof a desired output characteristic.

The MCU 129 is programmed to control the LED driver circuits 121-127 toset the individual output intensities of the LEDs to desired levels inresponse to predefined commands, so that the combined light emitted fromthe optical aperture or passage of the integrating volume has a desiredintensity. Dimming, for example, may utilize control of the intensitiesof the individual stings of LEDs in the array 111. It is alsocontemplated that the MCU may implement a step-wise dimming function byON-OFF control of the strings of white LEDs in various combinations, asdiscussed in more detail in U.S. Application Publication 2008/0224025 toLyons et al. If there are two or more colors of white LEDs and/ordifferent primary color LEDs, the intensity control by the MCU 129 mayalso control spectral characteristic(s) of the integrated light output.

The electrical components may also include one or more feedback sensors143, to provide system performance measurements as feedback signals tothe control logic, implemented in this example by the MCU 129, to insurethat the desired performance is maintained or to facilitate colorcontrol or the like. A variety of different sensors may be used, aloneor in combination, for different applications. In the illustratedexamples, the set 143 of feedback sensors includes a color and/orintensity sensor 145 and a temperature sensor 147. Although not shown,other sensors may be used. The sensors are positioned in or around thefixture to measure the appropriate physical condition, e.g. temperature,color, intensity, etc. One or both of the illustrated sensors could bemounted on the flexible circuit board, for example, on one or more ofthe tabs.

In a system using RGB or other combinations of multiple color LEDs, thesensor 145 could provide color distribution feedback to the MCU 129. Fordiscussion of the all-white example, we will assume that the sensor 145is an intensity sensor. The light sensor 145 therefore providesintensity information to the MCU 129. A variety of different sensors areavailable, for use as the sensor 145. The light sensor 145 is coupled todetect intensity of the integrated light, either as emitted through theaperture or as integrated within the volume of the optical cavity, e.g.in cavity 2 in the example of FIG. 1. The sensor 145 may be mountedalongside the LEDs for directly receiving light processed within thecavity. However, some small amount of the integrated light passesthrough a point on a wall of the cavity, e.g. through the Valar®reflector, therefore it may be sufficient to sense light intensity atthat point on the cavity wall.

The MCU 129 uses the intensity feedback information to determine when toactivate the sleeper LEDs 119. The intensity feedback information mayalso cause the MCU 129 to adjust the constant current levels applied tothe LEDs 113 to 117 in the control channels C₁ to C₃, to provide somedegree of compensation for declining performance before it becomesnecessary to activate the sleepers 119.

The temperature sensor 147 may be a simple thermo-electric transducerwith an associated analog to digital converter, or any of a variety ofother temperature detectors may be used. The temperature sensor ispositioned on or inside of the fixture, typically at a point that isnear the LEDs or other sources that produce most of the system heat. Thetemperature sensor 147 provides a signal representing the measuredtemperature to the MCU 129. The system logic, here implemented by theMCU 129, can adjust intensity of one or more of the LEDs of array 111 inresponse to the sensed temperature, e.g. to reduce intensity of thesource outputs to compensate for temperature increases. For example, iftemperature is increasing due to increased drive current to the activeLEDs (with increased age or heat), the controller may deactivate one ormore of those LEDs and activate a corresponding number of the sleepers,since the newly activated sleeper(s) will provide similar output inresponse to lower current and thus produce less heat.

In a typical general lighting application, in say an architecturalsetting, the fixture and associated solid state light engine 101 will bemounted or otherwise installed at a location of desired illumination.The light engine 101, however, will be activated and controlled by acontroller 151, which may be at a separate location. For example, if thefixture containing the light engine 101 is installed in the ceiling of aroom as a downlight for a task or area illumination type application,the controller 151 might be mounted in a wall box near a door into theroom, much like the mounting of a conventional ON-OFF or dimmer typewall switch for an incandescent or fluorescent light fixture. Thoseskilled in the art will recognize that the controller 151 may be mountedin close proximity to or integrated into the light engine 101. In somecases, the controller 151 may be at a substantial distance from fixturethat incorporates the light engine. It is also conceivable that theseparate controller 151 may be eliminated and the functionalityimplemented by a user interface on the light engine in combination withfurther programming of the MCU 129 (see e.g. the above cited U.S. Pat.No. 6,995,355).

The circuitry of the light engine 101 includes a wired communicationinterface or transceiver 139 that enables communications to and/or froma transceiver 153, which provides communications with the micro-controlunit (MCU) 155 in the controller 151. Typically, the controller 151 willinclude one or more input and/or output elements for implementing a userinterface 157. The user interface 157 may be as simple as a rotaryswitch or a set of pushbuttons, e.g. to control ON-OFF state and set thebrightness or intensity level (dimming control). As another example, thecontroller 151 may also include a wireless transceiver, in this case, inthe form of a Bluetooth transceiver 159. A number of light engines 101of the type shown may connect over common wiring, so that one controller151 through its transceiver 153 can provide instructions via interfaces139 to the MCUs 129 in several such light engines, thereby providingcommon control of a number of light fixtures.

A programmable microcontroller, such as the MCU 155, typically comprisesa programmable processor and includes or has coupled theretorandom-access memory (RAM) for storing data and read-only memory (ROM)and/or electrically erasable read only memory (EEROM) for storingcontrol programming and any pre-defined operational parameters, such aspre-established light ‘routines.’ In the example, the controller 151 isshown as having a memory 161, which will store programming and controldata. The MCU 155 itself comprises registers and other components forimplementing a central processing unit (CPU) and possibly an associatedarithmetic logic unit. The CPU implements the program to process data inthe desired manner and thereby generates desired control outputs tocause the controller 151 to generate commands to one or more lightengines 100 to provide general lighting operations of the one or morecontrolled light fixtures.

The MCU 155 may be programmed to essentially establish and maintain orpreset a desired ‘recipe’ or mixture of the intensities for the variousLED light strings in array 111 to provide a selected overall outputintensity or brightness. For a multi-color implementation, the MCU 155may be programmed to essentially establish and maintain or preset adesired ‘recipe’ or mixture of the available wavelengths provided by theLEDs used in the particular system, to provide a desired spectralsetting as well. For a given intensity setting (and/or color setting),the MCU 155 will cause the transceiver 139 to send the appropriatecommand or commands to the MCU 129 in the one or more light engines 101under its control. Each fixture 1 incorporating such a light engine 101,which receives such an instruction, will implement the indicated settingand maintain the setting until instructed to change to a new setting.For some applications, the MCU 155 may work through a number of settingsover a period of time in a manner defined by a dynamic routine. Data forsuch recipes or routines may be stored in the memory 161.

As noted, the controller 151 includes a Bluetooth type wirelesstransceiver 159 coupled to the MCU 155. The transceiver 159 supportstwo-way data communication in accord with the standard Bluetoothprotocol. For purposes of the present discussion, this wirelesscommunication link facilitates data communication with a personaldigital assistant (PDA) 171. The PDA 171 is programmed to provide userinput, programming and attendant program control of the system 100, forexample, to allow a user to remotely control any number of thesystems/fixtures.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

1. A light fixture for providing general lighting in a region or areaintended to be occupied by a person, the fixture comprising: a lighttransmissive structure forming a volume, the structure having acontoured outer surface, an optical aperture surface and a peripheraloptical coupling surface between the contoured outer surface and theoptical aperture surface, the peripheral optical coupling surfaceforming an obtuse angle with respect to the optical aperture surface; areflector having a diffusely reflective interior surface extending overat least a substantial portion of the contoured outer surface of thelight transmissive structure to form an optical cavity including thevolume of the light transmissive structure, a portion of the aperturesurface of the light transmissive structure forming an optical apertureof the cavity; a heat sink member having an inner peripheral portion ofa size somewhat larger than the outer peripheral portion of the lighttransmissive structure and having an inner surface at an angle at leastsubstantially corresponding to the angle formed by the peripheraloptical coupling surface of the light transmissive structure; a flexiblecircuit board, the flexible circuit board comprising: (a) a mountingsection mounted on the heat sink member, and (b) at least one flexibletab attached to and extending from the mounting section of the flexiblecircuit board, each flexible tab being bent around the heat sink memberand positioned between the angled inner surface of the inner peripheralportion of the heat sink member and the angled peripheral opticalcoupling surface of the light transmissive structure; and one or moresolid state light emitters, for producing light intensity sufficient fora general lighting application of the fixture, at least one solid statelight emitter being mounted on a respective tab of the flexible circuitboard and positioned by the respective tab between the respective taband the angled peripheral optical coupling surface of the outerperipheral portion of the light transmissive structure, wherein therespective tab holds said at least one solid state light emitter againstthe peripheral optical coupling surface of the light transmissivestructure for emission of light through the peripheral optical couplingsurface into the volume formed by the light transmissive structure. 2.The light fixture of claim 1, wherein at least a substantial portion ofthe contoured outer surface of the light transmissive structure has aroughened or etched texture.
 3. The light fixture of claim 2, wherein atleast any portion of the angled peripheral optical coupling surface ofthe light transmissive structure receiving light from the one or moresolid state light emitters is highly transparent.
 4. The light fixtureof claim 1, wherein at least a substantial portion of the opticalaperture surface of the light transmissive structure has a roughened oretched texture.
 5. The light fixture of claim 4, wherein at least anyportion of the angled peripheral optical coupling surface of the lighttransmissive structure receiving light from the one or more solid statelight emitters is highly transparent.
 6. The light fixture of claim 5,wherein at least a substantial portion of the contoured outer surface ofthe light transmissive structure has a roughened or etched texture. 7.The light fixture of claim 1, further comprising: thermal interfacematerial (TIM) positioned between the respective tab and the angledinner surface of the inner peripheral portion of the heat sink member,for providing electrical insulation between the respective tab and theheat sink member and for providing thermal conductivity to the heat sinkmember; wherein pressure created by contact of the at least one solidstate light emitter with the outer peripheral optical coupling surfaceof the light transmissive structure compresses the TIM against the heatsink member.
 8. The light fixture of claim 7, further comprising: one ormore vias formed through the respective tab, from a first surface of therespective tab supporting the at least one solid state light emitter toan opposite second surface of the respective tab; and heat conductivematerial extending through each via, to conduct heat from each solidstate light emitter on the respective tab.
 9. The light fixture of claim8, further comprising: heat conductive material forming a first pad onthe first surface of the respective tab, in contact with each lightemitter on the respective tab; and heat conductive material forming asecond pad on the second surface of the respective tab and in contactwith the angled inner surface of the inner peripheral portion of theheat sink member, wherein the heat conductive material extending througheach via through the respective tab conducts heat from each solid statelight emitter on the respective tab from the first pad on the respectivetab to the second pad on the respective tab for transfer to the heatsink member.
 10. The light fixture of claim 1, wherein each solid statelight emitter comprises a light emitting diode (LED).
 11. The lightfixture of claim 10, wherein each LED is a white LED.
 12. The lightfixture of claim 1, wherein the light transmissive structure comprises alight transmissive solid, at least substantially filling the volume ofthe light transmissive structure.
 13. The light fixture of claim 12,wherein: the light transmissive solid comprises two light transmissivesections joined together with a gap therebetween; and the light fixturefurther comprises a phosphor contained in the gap between the twosections of the light transmissive solid.
 14. The light fixture of claim13, wherein at least one of the light transmissive sections is locatedat the optical aperture surface of the light transmissive structure. 15.The light fixture of claim 1, wherein the light transmissive structurecomprises a container filled with a liquid.
 16. The light fixture ofclaim 15, wherein the liquid contains a phosphor.
 17. The light fixtureof claim 1, wherein diffuse reflections of light within the volume ofthe light transmissive structure optically integrate light from the oneor more solid state light emitters, for emission of optically integratedlight through an optical aperture of the fixture at the aperture surfaceof the light transmissive structure.
 18. The light fixture of claim 17,wherein the respective tab holds said at least one solid state lightemitter against the peripheral optical coupling surface of the lighttransmissive structure for emission of light through the peripheraloptical coupling surface in such an orientation that the aperturesurface of the light transmissive structure reflects a portion of directemissions from each of the solid state light emitters back into theoptical cavity by total internal reflection, for subsequent diffusereflection off of the reflector for optical integration within thecavity before emission through the optical aperture.
 19. The lightfixture of claim 18, further comprising: a mask having a reflectivesurface facing inward with respect to the volume, covering a portion ofthe aperture surface of the light transmissive structure in proximity tothe solid state light emitters, wherein the optical aperture is formedby a portion of the aperture surface not covered by the mask.
 20. Thelight fixture of claim 18, wherein the respective tab holds said atleast one solid state light emitter against the peripheral opticalcoupling surface of the light transmissive structure for emission oflight through the peripheral optical coupling surface in such anorientation that the central axis of emission of each light emitter issubstantially at an acute angle relative to the axis of the aperturesurface of the light transmissive structure and inclined somewhat awayfrom the aperture surface of the light transmissive structure.
 21. Thelight fixture of claim 20, wherein: the obtuse angle of the peripheraloptical coupling surface with respect to the optical aperture surface oflight transmissive structure is approximately 120°; and the acute angleof the central axis of emission of each light emitter relative to theaxis of the aperture surface of the light transmissive structureapproximately 60°.
 22. The light fixture of claim 21, wherein: thevolume of the light transmissive structure has a shape corresponding toa substantial section of a sphere; the outer peripheral portion of thestructure along the contoured surface of the light transmissivestructure is circular about said axis; an inner peripheral portion ofthe mounting section of the flexible circuit board is circular; and theinner peripheral portion of the heat sink member is circular.
 23. Thelight fixture of claim 1, further comprising an optical grease, glue orgel between the peripheral optical coupling surface of the lighttransmissive structure and at least one solid state light emitter forproviding refractive index matching relative to a material of the lighttransmissive structure forming at least the angled peripheral opticalcoupling surface.
 24. The light fixture of claim 1 in combination withcircuitry for driving the solid state light emitters to generate light.25. The light fixture of claim 24, wherein the flexible circuit boardincludes a strip extending away from the mounting section of theflexible circuit board providing electrical connections to thecircuitry.
 26. A solid state lighting system for providing generallighting in a region or area intended to be occupied by a person,comprising a light fixture and drive circuitry, the fixture comprising:a light transmissive structure forming a volume, the structure having acontoured outer surface and an optical aperture surface; a reflectorhaving a diffusely reflective interior surface extending over at least asubstantial portion of the contoured outer surface of the lighttransmissive structure to form an optical cavity including the volume ofthe light transmissive structure, a portion of the aperture surface ofthe light transmissive structure forming an optical aperture of thecavity; a heat sink member having an inner peripheral portion of a sizesomewhat larger than an outer peripheral portion of the lighttransmissive structure and having an inner surface at leastsubstantially conforming in shape to the outer peripheral portion of thelight transmissive structure; a flexible circuit board, the flexiblecircuit board comprising: (a) a mounting section mounted on the heatsink member, (b) a strip extending from the mounting section of theflexible circuit board providing electrical connections to the drivecircuitry, and (c) at least one flexible tab attached to and extendingfrom the mounting section of the flexible circuit board, each flexibletab being bent around the heat sink member and positioned between theinner surface of the inner peripheral portion of the heat sink memberand the outer peripheral portion of the light transmissive structure;and one or more solid state light emitters, for producing lightintensity sufficient for a general lighting application of the fixture,at least one solid state light emitter being mounted on a respective tabof the flexible circuit board and positioned by the respective tabbetween respective tab and the outer peripheral portion of the lighttransmissive structure, wherein the respective tab holds said at leastone solid state light emitter against the outer peripheral portion ofthe light transmissive structure for emission of light into the volumeformed by the light transmissive structure.